Judd, this won't answer all your questions, but it might help. I started fighting this battle in the same timeframe, with the same car, and with the same objective. I've done ~25 track days since embarking on this effort to make my car a better track car, while remaining reasonably streetable. Some of my mods have worked, some have not.
1. Suspension. The problem was that the car was understeering like a pig. I went with ROW M030 and stock alignment. That helped. Then I went with GT3 "Street" alignment (-1deg camber F, -1.5deg R). That helped even more. Now I'm about to dremel the front strut mounts to try to get a little more neg camber. My tires are wearing very badly on the outside corners, a good indicator that more neg camber is indicated.
If I had to buy a suspension again, I'd buy something that dropped the car more. The would require that I pour some cement so I could get into my garage, but that would be a small price to pay to drop my center mass another 10 or 15mm, and the additional neg camber that would result.
When you say M030, it's important to distinguish between US and ROW.
I have read postive things about putting monoballs in the shock mounts, but I've heard that it can be tricky. I've read about ball "fit" problems and increases to "height" that were unexpected. I'd certainly buy the monoballs from the same outfit that I got the shock/struts from.
If you would like to do any SCCA "Solo" or NASA "Time Trial", be sure to understand the impact of your mods. External reserviours and adjustatibility, for example, can count against you in Time Trial.
2. Seats. I did a lot of research on this. I'm curious as to what you ended up getting and how well it worked. I ended up concerned about the width of the seat narrow enough. I think that the OEM seats were ~18" and most of the seats I found on line were 21 or 22". Note that I had to get seats that folded forward. I ended up with Corbeau A4 "Narrow", w/ anti-sub slot. They worked out ok, but not without warts. They are a very tight fit against the central tunnel, they don't slide far forwards or backwards, and the headrest pushes my helmet forward akwardly. I also had to get the butt and lumbar pads removed and replaced with much softer foam.
3. I ended up putting in a harness bar and 5pt. This was a huge step forward in holding me planted in my seat. But I'm going to be less excited about the 5pt if the car rolls and the roof pushes in and breaks my neck.
4. Tires and wheels. I've spent most of my track days on Yoko AD07's 225/285, but I've just bought an extra set of wheels and put on Yoko AO48's in 235/295. I spent a lot of time trying to figure out how to go to a wider tire, but in the end I was defeated by the cost of wheels with GT3 offsets and some uncertainty whether or not wider would work. By a narrow margin I found a consensus that GT3 offsets would be necessary to wider. And that consensus was amid a heck of a lot of contradictory or amibiguous info from well informed sources. So in the end I decided that the lower cost (996 offset) and more "sure" solution was the smart way to go. Hence 235/295.
5. Even tho it's easy to drive a street/DE car to a distant track, start thinking about trailering it. I blew my motor 7hrs away and having no way home didn't make things any easier.
6. Is "dual use" the way to go? I'm starting to think that turning my street 996 into a street/track 996 just makes it crappy for both. I'm thinking about getting into Spec E30 and putting the OEM seats back into the 996.