Have you tried giving him hay while tied?
Have you tried just single tying him to one of the cross tie rings?
Have you tried tying him in his stall and tacking him up there?
Have you tried putting a set of crossties in his stall and tacking him up there? It’s very common to what he’ll have experienced at a show.
Have you tried lunging him, riding him, putting him up, then pulling him out and riding without lunging?
Have you tried not lunging him, getting on and going straight to a trot? Then walking later?
You say you have not really been getting after him if he moves around, what if you change that? My new mare moves around a lot in the cross ties and will back up until the ties are taught. She doesn’t pull back, she just stands there and strangles herself. I didn’t make any progress until I started carrying a metal shedding blade and thwonging her with it when she backed up or got into my space. It makes a very satisfying noise and vibration. She’ll jump around quite a bit and look at me like I just let a mark but it has been working.
I feel like a big meanie because I also thwong her for kicking when I blanket her or girth or up, and I thwong her when she tries to mow me down but I’ve noticed a much more respectful change in behavior and she has calmed down quite a bit. If you start to act like the alpha leader, take charge, tell him where to put his feet at, and tell him to not worry about other things because you are on alert he might calm down.