I hadda fix some things in World 1 to get to World 2, I stopped when I got stuck in the pyramid level when I got the Hammer Bros. suit with no way out, with that said there should be no dead ends where you get stuck, you have potential in the level design department, I kept on playing.
I can mentor you in designing levels and map designs if you want, I also have an IPS patch that gives the soundtrack a darker tone thanks to Nicole from the Kafuka Boards. I do like your graphic changes, one suggestion on the dungeon level in world 1, change the palette it hurt my eyes a bit and change the lava palette back to it's original palette.
Which SMB3 editor are you using, SMB3 Workshop or SMB3 Foundry?
I also have a few dead SMB3 hacks from the early 2000's, if you wanna use those levels in your hack. Gimme a holler, I'm poking at various projects behind the scenes so a project like this will motivate me to hack full steam again. Take care, bro.