Maybe you should mention that this door should act some non solid tile like 25 or bush tiles, otherwise i can't spot errors WYE
Oh yeah, right - 25 is what the block should act like, not any kind of door.
On another note, I just realized I didn't actually need to do the X register math in ASM when the assembler could have done it just as well - you know, LDA $19B8+!ExitToUse instead of LDX #!ExitToUse : LDA $19B8,x. I don't think we're so low on space that we'd need the four bytes I've wasted, though.
tl;dr: everything's still fine, I'm just rambling.