I did not get the sense from the OP's post that she wants to move in with him, but just to move closer to him and live in his city. And we do not even know whether or not his other relationship is with someone he lives with, so jumping the gun a bit there.His partner that it doesn't seem you know much about at all will (be in the same house?) have significant power over the stability of your living arrangements . . . Make sure you can live with him.
Then to start my response, I'm sorry for misunderstanding your choice of methods in your move. I don't want to offend, I'd like to help and in trying to help I do my best to be forwards and to the point.