This hack wasn't that bad, but there are a few things you'll need to fix before we can approve it.
It seems that you haven't changed Mario's title screen movements, so he acts quite strangely sometimes. I suggest you to edit Mario's movements so it would look more 'normal'.
You need to work a bit more on your message boxes.
Also, the spacing in the first message box is a bit weird. I suggest you to get someone who can help you fixing the messages.
Not a really big deal, but you forgot to put the "below bush" ground tile here, causing a small cutoff.
Missing wall tiles there.
You should block the way to the slanted pipe, like Nintendo did.
Isn't this a bit too hard for the first castle? Precision jumps usually aren't big fun...
I found this trap quite unfair, you really shouldn't put back the player to the very beginning of the level just because he/she picked the wrong path. It's a pretty lazy solution.
So, that's it, I'm sure you can fix these easily.