Good for you. Can you call health department /housing department anyway to report the mold? it would be nice to see this guy's face. Even when he paid you he is still in trouble! oh my ! when he thought he had bought your silence... lol.
I mean if I had an apartment that may be a health hazard I would NEVER ask anyone to live there.
Unfortunately it is very common, some landlords often threat or give any kind of excuse not to give back the deposit, or claim the apartment was in perfect conditions when it wasn't in the first place.
I also had an old lady threaten me when I left an apartment, yell, nag, and treat me horribly when she was the one who owed me. I try to think it all ends up about them being hungry and needing to pull that kind of stuff because they are desperate. Sad.
Anyway good for you for moving on! I hope you found a better place.....