The loss of control when you speed up is entirely intentional! Specifically, slowing down halves your speed, but doubles the amount you can curve, while speeding up doubles your speed, but halves your curve.
We've gotten a few people mentioning the resolution issues and that's on me (runBAMrunfaster) for not being up to snuff on how unity handles that sort of thing. One of many things to tweak and fix post-jam! More content is definitely on our mind, and I think we both plan to continue tinkering for as long as either our or other people's interest in the project last; whichever lasts longest.