Keep an eye out for the next Autox School, you get more seat time than a normal autox event and instruction on car control (best of both worlds). Most of the Houston Region SCCA autox events are on Sundays, so they should work with your schedule.
I was able to start out as an "intermediate" driver at the track thanks to my years of autox (I had 6+ years of heavy autox with nearly 200 events before I made it to the track). My first 'trackday' was one of the very first SCCA Track Night in Americas, a couple of my autox buddies were going and they tried to get me to sign up for the 'advanced' group but I signed up for the 'intermediate' instead, my next event was a PCA Time Trial, and the next HPDE I went to was short on instructors so I got default promoted to solo intermediate. When I finally got an instructor on my 4th trip to the track, he helped me fix some bad autox habits (turning in too aggressively, not be smooth enough, and only looking half as far ahead as I should have). I knew there were places I wasn't driving as well as the car could, but without the coaching I didn't know how to fix them on my own (other than trial and error, which is slow going and risky). I had car control and feel down, so I was miles ahead of non-autocrossing novices (if you've done fewer than 50 events, or if it's been more than a decade since you competed, you are essentially starting form scratch).
I've instructed a few of my autox buddies, and I can get them to the level of a fast solo intermediate driver by the 3rd-4th session thanks to their autox skills (this level of progression would normally take a competent/skilled novice 2-3 events, an average novice 4-5, and some occasional (3-5 events per year) track people never progress beyond this level of skill). A year's worth of autox costs about the same as single weekend of HPDE but will definitely allow you to learn more. I recommend everyone who wants to get fast at the track does at least a dozen autox events (you can do autox and track events in the same month/year, so you don't have to choose one over the other).
There are a few ways to get fast:
1) start karting and/or motocross at a young age (before you start driving cars), spend lots of time on dirt/snow learning car control, then do 6-10 track events
2) be a competitive kart/motorcylce racer first (iRacing or simulator stuff helps, but it isn't near as effective as actual driving)
3) do autox until you are competitive (typically about a dozen events) then go to the track (it'll still take you 6-10 events to get truly fast, but you'll be competent after the first couple of events)
4) do a minimum of 6-8 track events for about 3 years with instruction for at least the first 2 years
5) do 3-5 intensive driver training schools (like Skip Barber or Dirtfish) then do another 6-10 normal track events
You are down to the last 3 options and your schedule probably eliminates the last option. So, you can spend you time and money slowly progressing (or not) at the track or you can learn your car control at autox while learning to drive on the track. Doubling up on autox and track events will shave about a year off your progression curve and allow you to better utilize your on-track time (you don't automatically become a good track driver, but you start with a huge head start).
Lastly, driving skills are perishable (especially while you're still in the early learning phases), so if you go 3-4 months between events you'll spend at least half your time relearning what you've forgotten.
0 - new to driving
1 - competent street driver
2 - Novice, you've done one track day and/or a few autox events
3 - Repeat Novice, you've done a couple of events and you know terms like apex, turn-in, track-out, and that there are corner stations with flags (you don't always look at the flag stations, you don't immediately give/take point-bys, and you don't know where you are supposed to put your car for about half the corners) you are still learning the fundamentals of car control
4 - Experienced Novice/Intermediate (usually the 2nd or 3rd event for the typical driver), you are safe on track but not fast. You do some things right but there's still plenty to work on (this is where most of the autox guys start)
5 - Progressing/developing Intermediate (seasoned autocrossers get here after a trackday or two), this is where you are trusted to drive solo but benefit greatly from coaching), you can give and take point-bys effectively without losing much pace, you see most flags, and you can adjust to take corners off line when necessary. You are safe and courteous on-track and can be trusted to drive without an instructor. This phase could take awhile, you are developing a sense of where you are supposed to put you car for most corners but you don't always get there, or you can hit your marks but only at a slower pace. A large percentage of trackday drivers fall in this category.
6 - Fast/skilled Intermediate (not necessarily in a group called 'intermediate', this group includes people in 'advanced' run groups), these people have either an intellectual or intuitive knowledge of what they are supposed to do on track but not both. They are comfortable and safe in most conditions/scenarios. They may have a couple of corners that they are still figuring out, but they know what they are doing. These drivers are good with their home track but will take a few sessions to adapt to a new track or a couple of sessions to relearn a track/configuration they haven't driven in the last year. These drivers also are uncomfortable and slower than others in their group when conditions are poor (especially in the wet). This is where people end up when they've been at it for a few years but aren't actively trying to continually improve, there's no problem/shame hanging out here and a lot of nice/friendly people you meet at the track fall into this category.
7 - Skilled Amateur, this is where the "fast guys" classifications begin, these people know where and how to place their car and can find and drive near the limits of grip. They might have one or two bad habits or problem areas but they actively seek out ways to get faster (through data analysis, interactions with other skilled drivers, and riding with/getting help from other fast guys). At this level you can start instructing after a little training if you so choose.
8 - Instructor/Coach, you know car control and can figure out where to be on track to go fast. You can adapt to new tracks and situations quickly and you can explain what to do, why, and how. You don't have to be the fastest guy on the track to be in this group and you don't have to be a flawless driver, but you have to have a mastery of car control and both an intellectual and intuitive knowledge of track driving. This is the classification where the driver will be fast regardless of what they are driving.
9 - Champion/Seasoned Competitor/Semi-Pro, when you get to this level you will know it and you probably won't be showing up to many DE's anymore (you don't have time and/or you are focused on a series/goal for anything but your competition). You might moonlight as an instructor, show up to test out setups or master a new track before an event, but you are far more serious than the rest of us.
10 - Professional, you get paid to race/drive. You set lap records and make the rest of us look like the amateurs we are.
11 - The Stig/Star driver. People who don't own a fire suit or have stacks of tires in their garage/house know your name. People have asked for your autograph.
Talley, sounds like you are at a 1.5 or a 2 and you want to get to a 5-6 relatively soon. If all you do are trackdays, you're looking at needing a minimum of about 6 track events with good instruction (add in one additional event if you go longer than 60 days between events). You are going to have a hard time learning in your Mustang at the track, it isn't a novice friendly vehicle and you won't be driving it enough to get comfortable with it quickly (you'd acclimate faster if it was your daily driver but I wouldn't recommend that as a strategy). You are basically trying to learn how to juggle and starting with chainsaws. Sure, they aren't running and you are only starting with like 3 of them, but if you started with some beanbags (a Miata) or tennis balls (any sub 300hp street car) you could probably master the basics with much less difficulty, danger, and cost.