I know my question has been asked over and over, however, I cannot find a good resolution.

So, my floor is off by 9/16. The drain side is lower than the back. As of right now I have my stringer/ledger board level. If I keep everything as is, the front apron on the drain side will have a 9/16 gap. What to do?

BTW: the subfloor and tile does not butt up against the front apron of tub. However, I can remove the tile and then butt the tile up against if it will help.

The best way would be to figure out why the floors not level and fix it from below the floor first or this can come back to bite you on the butt on everything else you try to do.
A gap that big can cause the tub to flex and crack.

been there done that
install your stringer leval
put tub in leval. shim with treated wood. under tub
at the apron, shim with cedar door shims.and cut flush
if crack is groutable, grout it. then caulk
if crack to big. cover crack with a 1/4in x 2in vinyl base board strip. at bottom of apron.. same color as tub
if thats not agreeable to home owner. chip the floor out and start over
if its a conventional "wood frame" foundation
fix whats wrong. leval floor
if tub is out 9/16 the the toilet is leaning also
9/16 will make you slip off toilet and get wet

This message has been edited. Last edited by: Frodo,

fix the floor. don't shim and pray here. the alternative to fixing the floor before you pour all that time and money into the bath is fixing it later when it's worse, you lose all your previous work, and possibly if the problem was a major one, having to do a lot of gut and rebuild.

put another way... it may be cheaper and faster to touch up the X-rays than cut out the cancer, but it will bite you in the end.