Looks to me the guy is pissed off at YOU for some reason.
Probably because the other guy expects legal tender as a form of exchange for his services, but SimonTaddio_Qc decided to offer him equipment "he considered a deposit" as a form of barter (would've worked perfectly in the 19th century). The whole thing sounds like two playground kids discussing over candy. Just talk to the guy and get to an arrangement, which, by the way, should have been set since day 1.
Concerning the YT stuff, don't worry. Not a lot of people gives a crap about random DI's that are impossible to find through a Youtube search due to the fact that the videos' titles are not specific enough. When I read "my music has been stolen" I immediately thought of what happened to Ola Englund... If he wanted to steal/give away your ideas, he would suggest some of them to his clients if your stuff happens to fit the clients' compositions. Well, actually, maybe he is already doing so.
About the copyright, I don't know how it works in Canada, but I doubt that any random shit that comes across your mind is automatically registered to you and only you just for being a member of the SOCAN. It sounds a little fantastic, honestly. But if you are sure about that, then you should report this case to whom it may concern.
And by the way, thanks for never getting back to me and my partner for the logos we did for your band. Even though we didn't agree on anything, we expected at least some sort of "thanks for working 3 weeks with us trying to comprehend our unclear, unspecific ideas. Unfortunately we decided not to use your logo proposals". I am going to assume you are a honest Canadian and won't be using our ideas for your future logo, as you wouldn't want someone stealing your work. Either way, such logos are registered (for real).
If I were you, I would consider learning how to work with people, because clearly you don't. Best of luck with your problem.