so i ended up
cutting the baseboard
the back of the vanity was a wood beam so i would have had to cut the entire back support which was not do-able
i nailed the wainscotting behind the vanity to the wall everywhere so it doesnt slip down. removed the baseboard, cut it and installed the vanity
the vanity was still not flush with the wall, but i ended up sticking a thin piece of plywood behind the vanity top to bring the gap to nothing. then screwed in everything and now the vanity is nice and stable
thanks everyone for help!
the bathroom is looking sexy!