I found my tardis partly in the floor, each time i move it, it stays like that, but not when I move it on the ground.

This is a bug with slabs. I assume it's sitting on a floor made of slabs / doubleslabs?

I believe this bug has been fixed by Josia for Update 58.

Ok, thanks. Oh and one other thing, I just remembered. No matter how hard I try, I can't get it changed. My actual Minecraft username is TheCollossalDan.

Minecraft usernames don't update on the site, sorry about that. Everything still works though, so don't worry. The site knows your updated username.

Ok.