What a creative little game!
I need to draw a chart of the font to become a pro gamer at RuneDuck :)
I’ll second the other comment about making all the letters uniform in width. It’d feel more intuitive if, say, “E” covered the same cells as “F” plus the bottom bar.
If you’re worried about the middle-left and middle-right columns not being hit as often, how about making the vowels bold? Something like this perhaps:
AAA EEEEE IIIII OOO UU UU
AA AA EE I OO OO UU UU
AAAAA EEEE I OO OO UU UU
AA AA EE I OO OO UU UU
AA AA EEEEE IIIII OOO UUU