I'm really glad you liked it and thanks a lot for the good words. I personally like old school stuff that's why I also like to give that vibe into my games. Let me explain the stuff you mentioned about the game.
The exit button needs to exist and will be there in the next update. The restart button just restart the game like you exited and reopened it again, I haven't bothered yet to add a save option hahahah. I tested the truck setups many times before publishing it and they work. Maybe it needs to have some kind of indication to let you know that the the settings changed. Definitely will be there in the next update. If you'll play the game again when changing the truck setups notice the differences in suspension or power. For example try to climb something with the "original".
Thanks again! Have a good one!