Come to think of it, I don't think I ever played SMB2. So I don't really know. I'm just going off of what games I have played and what feels 'natural' to me. I'll give it another run through later, see if maybe it just takes a bit to click. As for the boss, I agree. Just a little something to spice up the fight a bit is all I feel it really needs. No need to rework the whole thing, disregard that.
I look forward to seeing your progress.