I'm sorry that you had to witness your h's new toy and the truck canopy. It does appear that he's settling in, but you have to remember that he's in replay and he's going to be making this place his own for a while. If you reconcile, all of those things can be moved back home and the canopy either stays there or is sold. Nothing is permanent right now w/him or his living arrangement.
Sure, it makes you angry because it looks like he's planning to live there for a long time...but I don't think that's going to be the case. Right now, he is living in a fantasy world. He's like a kid decorating a tree house and wants to put his stamp on it...he's seeking approval from the two important people in his life and it appears that's you and your son.
Replay can take anywhere from 2-3 years or longer if they've not dealt w/their issues. Live your life to the fullest and leave the door ajar. Nothing says you have to wait on him to catch up. Also, looking/analyzing your h for any signs that the old h is coming back into the world, is like watching paint harden.
As for being friends w/him, you can be civil and treat him like the man next door. He can't miss you or the relationship if you are readily available. He has to learn to do things on his own w/his son and that includes missing family holiday dinners, etc. Right now, he's got the best of both worlds...I think it's time that you limit the amount of time that you are spending w/him. I wouldn't be too quick to respond to his messages. He can't miss something that is still there and within his grasp. Start distancing yourself just a wee bit and watch the changes take place.
I know you don't want to send a message that you are done...but why should he be concerned about you and the relationship, if nothing has changed except the living arrangements? It's time to do some 180's and live your life and make plans for YOU. If your h wants to be a part of YOUR life, then he'll start to notice the changes and begin to try to catch up.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.