Cheat then, cut corners, do whatever you need to reduce polycount while keeping up appearances.....

You don't need to boolean and connect everything together. Overlapping is ok as long as yourr not trying to make decals (Z-buffer still fights with those)

Those red walls... you've got at least 9. so thats about 9*2*2= 36 polygons there... you can do with with just 2.
The blue floor... 2 there too. (maybe 4 if using symertry)
the light blue cylindar on the bumpout on the wall? Stretch the entire cylinder all the way from one end to the other.
the blue, green and yellow bumpout on the wall.. it can be done with 6 polygons.
same with the yellow on the floor area... 2 polygons
the green dividers... 6 polygons will do.... assumin' it's flat on all sides.
Edit: Did this 'ere pirate talk mess up IMGs?
Double Edit: Wait? your having problems lack of UVmap space or too many polygons?
Triple edit... hahah pirate talk change cheat.jpg to swindle.jpg
Plus if you editted your message, pirate talk won't disappear.
Also you can get rid of any polygons that the player will never see.