I already fixed most of your issues (including the semi solid platform bug), but of course I can't update the game because it's a game jam... xP
The reason the controls feel off is because you move slower to the right than to the left. This is to simulate running, instead of driving a car. (Wich means constantly driving forward, and only changing how FAST you move forward)
It's something you really gotta get used to. So I get why you feel this way! (Might actually change that)
Also, I was surprised you didn't mention anything about difficulty! Usually in these kind of games, the game goes faster and faster the longer you play. (I'm working on that right now.)
also i just want to say that the permanent upgrades almost werent a thing because playerprefs is hard to work with lol