Yes, the asterisk, braces and pipes gave me consternation, as well as the similarities between D and O. But I was determined to use the Kenney fonts I had, and that seemed like the clearest of the bunch. Originally, the enemies spawned high enough that the words went right off the top of the screen, so being covered by the score was an improvement. :P I'll definitely get them to spawn lower, after I've given the "this is what came out of the jam" version to settle for a bit.
During your game play, I remember you mentioning the backspace. I love the backspace so much, it's ruined my typing because I'm just ALWAYS fixing things as I type. So it's part of the "TYPE IT RIGHT" idea of the typing tutor scheme. But after watching you play, I thought about maybe adding backspaces as a buff or power-up. Not sure if that would help, or just confuse things more...