Sounds like your super-DIY friend might like to help. Next time, say
"well, what do you think?" and see if he can offer something helpful.

A competent DIY should be able to take a look at the framing, the
joists, walls, etc., and decide if the thing is possibly load bearing,
and to what degree. A bathroom wall even if perpendicular might be
extraneous. Or, of little enough value that just adding a short beam
with two posts (hidden in the adjacent walls) would be enough to take
care of the floor above. But noone can tell frome here.