A) which team would win: Freddy/Jason against Slayer/The Gholam? and

Freddy/Jason. Jason is more lethal than the Gholam - he can't be killed, whereas the Gholam can - it's just extremely difficult. Freddy is much more powerful than Slayer in the dream world - he isn't a mere assassin with a few T'A'R abilities (ignoring the fact that T'A'R as a dimension may not even exist where they will fight); he could easily destroy Slayer in the dreamworld whereas the dream demons would keep reviving Freddy if he is incapacitated there.

B) who would win a one-on-one round robin tournament involving all four?

It would come down to Freddy vs. Jason, because their powers are god-like in comparison to the WoT villains. I think Jason would win in the end, because Freddy may very well need to go into the real world to confront him, and he has normal human strength in the real world. Per the last movie, without the three dream demons to revive him (which only works in the dreamworld), he was killed by a heroine.