Yeah that's better with the curve! Fun fact. Did you know the difficulty curve originated from a glitch? Atari's Space Invader's had too many enemies on the screen causing slow-down. As you removed them from the game, the game sped up lol.
Having to reload unity is a pain. No need for a menu now, but I'd try something like on2dcollision(){ //loadScene("game");}. Just for a quick restart.