First of all: Thanks for uploading more screenshots. I find this rather important to get a first impression of the hack.
So i played your hack a bit (finished the boomerang bro level).
Your hack definitely isn't bad! I'm unsure though, if i should call it "good". Here are my complaints:
1.) I'd say the levels are too long, especially if this is really considered to be a first world. Personally, i'd shorten every level by a few screens (3-8 perhaps). I think the levels would be more fun to play then, since currently some of them more feel like a trial of patience.
2.) Don't use so many invisible blocks. It's okay if you use them here and there, but i get kinda reminded of old kaizo due to their current amount. I'll also note, that "bridge- or stair-building" isn't very interesting either and gets tedious quite quickly. I especially noticed this in the castle. Please avoid this kind of level design.
3.) In the first real water level the sprites looked cutoff several times
(i think mainly when bloopers came onscreen).
These are my 3 main complaints. As said, your hack definitely isn't bad, but it didn't feel outright fun to play and since this should be the main aim for every hack, this leaves a slightly bitter taste to mean. I'm optimistic though you are willing and able to improve, so i'm looking to see more of this. In the end, having Monty Mole instead of Mario as character was pretty cool (even if i couldn't discern if i was small or big). However, good luck with this hack!