I think you had some great ideas, however I think the main thing you need to work on is not forcing a difficulty level.
This is tough to do though. The actual level design is good, and the aesthetics are good, but all the 1 tile jumps are a bit much.
In Gruesome Green, the first goomba to 2nd is a little snug at times, little funky jumping off yoshi, it's not bad, and it might not even need changed, but I would play around with the yoshi placement just to see how it feels in different spots.
From there I might think about making the 1 gap openings into 2 gap openings, that is the big thing about natural difficulty vs artificial difficulty. It's possible though, to keep the 1 tile gaps if the muncher on the right side above the wiggler were removed, its really snug getting in there. If that jump were not as snug it wouldn't be as bad having the 1 tile gaps to jump up thru, since there would be an extra split second to reposition.
After the midway, the only thing I think might be to add 1 extra space before the paragaloomba in order to throw the shell up and recatch as to not get frame-ruled on the galoomba.
Thats about it on that level, just a few artificially tough feeling spots, other than that good design.
In the 2nd level, the beginning is neat and not too tricky once learned, possibly try the 4th flying koopa to the left 1 more tile for smoother alignment with bullet bill,the 1 tile jumps down thru the munchers are tight considering what came just before. Other than that, I would just play around with the end section, waiting for the one koopa meh
This is totally Kaizo Light, and minus just a couple tight spots, I'd call this the easier side of Kaizo Light.
Overall so far so good I think, and the aesthetics are good. That lime green really pops out against the background
PS I found your planned secrets in LM