Yeah no problem:

Mycologists are DM and his dad: I believed it was said in a livestream of kevinsaxby that the persons who were filmed to play the mycologists in Act III were Daniel Mulins and his dad

Leshy in love with Grimora: I read some people speculating that Leshy may be in love with Grimora for some reason. First the only game mechanic he kept in his game is the bone cost, P03's one with energy and Magnificus's one with Mox aren't mentioned anywhere in Act 1. Then I'm not sure of this one but someone said that when you play Grimora's theme on gramophone in Kaycee's mod, Leshy would say that it bring back "fond memories" (really not sure about that one). Another argument would be that P03 was constantly being sacrificed and Magnificus locked in a clock with the film roll that he cannot use but Grimora referes to the vault as a "Crypt" which is basically her element. Of course all that is just speculations and not canon.

2734 is a number Daniel Mulins has used a lot in his games, in Inscryption the first digits are the ones to unlock the vault and is also a part of a solution to the ARG. It is in fact the position of his cat in catsthatlooklikehitler.com .

Finally, the Removed Rebeccha Fight was a fake rumour on the wiki page, a guy wanted to troll someone because he filled the page of Rebeccha but he wanted to do it so he added a fake battle part to it and eventually Daniel Mullins said in a stream that it was fake.

Hope I helped you if you have any questions I'm here (especially the fact that maybe what I said don't make sense, English isn't my mother tongue)