Did your race org sanction the Schroth with your Recaro without a harness bar?
I'm looking at Sparco QRT seats right now, a Krause harness bar, Sparco 6pt harness and the other bits to mount the seat. It'll run me about $3k per side and obviously it'll be a lot harsher driving around on the street.
I've had a Lund 93/FF/E85 tune on my 2015 for years. It's awesome. But, I also haven't dealt with them in a number of years, so I have no idea what's going there. I haven't needed to. No issues with my tune. 2015-17 JLT, LU47 injectors and 2018 ported intake manifold. Stock exhaust manifolds and...
Man, I did it all. And I found out what worked and what didn't - later. Lol If you wanna do it, go for it. Maybe start with the BMR CB005 or Steeda subframe bushing lockout.
Then, I'd probably hold off on doing more upgrades until you know what you're trying to improve. Try a track day or autocross! It's really fun and you will actually be able to see what yourself and the car are capable of.