OP, if you’ve only been working with the horse for 30 days, you are probably expecting too much, since he had a year off.
I try to work on things one gait slower than where the problem arises. For example, my mare HATES to counter canter - it’s hard for her and she is very unbalanced. So we are jogging circles with a counter bend to help her shift her weight back and move her shoulders laterally. And although she neck reins (she is 7 too), I put her back into a snaffle and I am riding 2 handed while working on counter canter.
I understand you need to go to a full bridle at his age, but you won’t be doing him or yourself any favors by rushing into it. He’s telling you that he is not ready. You sound like a very competent rider, just need a little more patience. And I did have my mare in a twisted wire for about a year - she was diving into my hands and pulling on me. In that bit, she stopped that behavior.
