everything happening at once

I have lived my whole life in old apartments, houses, lofts... thought I had seen it all. But now- this is new for me-- the scene-
Upstairs bathroom in a house built in 1945, not updated since early 90s.
If I flush the toilet- sometimes just fine
but usually, water runs out between toilet and floor, pooling on the floor to 1/2 inch depth and also in downstairs light fixture.
If I run water-
sometimes fine
sometimes it causes water to run out between toilet and floor, pooling in that same fixture.
run tub- no problems seen
BUT
after water runs out between toilet and floor, icky watery brown stuff backs up into tub to as much as an inch. (not using tub anymore because of ick factor)
No problem with basement full bathroom, washer, dishwasher.
Called a plumber. He caukled around the toilet, and snaked the toilet and tub and pronounced it fixed. a few days later, it all starts up again.
Somebody help me please.
interesting side note- if a man uses the toilet, it usually works, if a woman, it usually doesn't

You simply have a partial clog in the main drain line causing this backup. I'm amazed that the plumber didn't open a main drain clean-out plug and snake the main drain line.
You can rent a heavy-duty plumber's snake, open a main drain clean-out and snake the line from the house to the street or septic tank to solve the problem (unless you have sectional drain line, such as cast iron, and then it may be a root problem, which would require "roto-rootering").
Good luck!
Mike