It seems like matrix/element has broken/removed self DMs. To bypass this, I had to make a brand new acct and DM that acct.

Element. Because element has been lying to you from the outset about how matrix works. You can just make a room with encryption + dm flag and not invite anyone. Though I'm not aware of a client that can do this. But syphon can in two steps; it can modify dm flag after creation, in room settings.