Took awhile, but after scratching my head for too long, I just kind of starting using my shoulder to ...persuade... the vanity to f'ing move. And it did. But more importantly was where it it did NOT move. Which was against the reefer wall.
A few more UMPHS! and I was able to get a hacksaw blade between the finished wall and the wood cabinetry.
3 on the top:
And 3 on the right side:
The top screw in the side mount I just could not get the cabinet to deflect enough in order to insert the blade: and I did not want to bugger the wall finish. After due consideration... I just gave it a mighty tug and pulled the threads out of the wood, leaving the screw:
When I get the flooring done, I'll drill several holes from the toilet room side of the wall, thru cabinetry trim, and into the reefer wall; should be at least as strong as the AS method; and LOTS easier for the next guy...
The toilet room, naked:
Spent about 2 hours getting the fricken closet flange off - seems the PO did not have a proper rubber gasket - so it looks like he used the boat builders friend, 3M 5200. Then it took another r2 hours to get the 5200 "gasket" out of the holding tank flange.
Ended up buggering the closet flange getting it off, and it seems neither my local RV store, nor Tucson CW carries them. Say what???
I guess no one ever replaces toilets or flooring in an RV around here...
Next problem is to figure out some way to wrap the sheet vinyl over the 90 degree platform top. I'm thinking I will need some kind of stair nosing: I can's see the sheet vinyl making that turn and staying in one piece for long.