I also don't have dyslexia, but I was struggling a bit letter editing level and I didn't want to spend too much time on it
For the shield I tried using it while moving and I think I was running into bullets on my top/bottom.
Then if I tried using it without moving I'd block 1 or 2 bullets in the burst being fired at me, but then get hit by the 3rd
So I stopped using it and just focused on dodging
The TD levels could be a bit longer, but I guess that goes against the theme you're going for, which means you'd probably have to keep adding new stuff to keep it interesting. I'm a sucker for them in general, so while I like them, I might be a bias'd opinion
'Difficulty' was kinda a hard thing for me to judge with a lot of these mini-games. In a lot of places the humor is very clear so when a level was super hard (to get a perfect score or to clear in general) I wasn't sure if it was intentionally difficult for the humor, or just to keep things interesting, or just being early in development. (it'd probably be more clear with more stages)
That all said, your game reminds me a lot of Warioware (with all the quick minigames) which can still be fun when things move slower and the games are a bit easier. So I think you could get away with slowing stuff down without losing the fun.
Of course idk what your plans are, if you add difficulty settings or stages that ramp up in difficulty as they go on it might not matter
Like the music you picked btw, it's a good fit
Good luck with it!