I have been playing with the TRT Method for groundwork and I think you might find some lessons there a bit helpful, potentially. Even the free facebook ads may have some ideas for you.
I am working with a horse that learned she could pull away from little kids. One thing that really helps me is to have a couple of lengths of lead rope for different situations. I’m using a 12’ with her right now, but if I’m out in the open with her or in a situation that might be scary or tempting I might use a 15’ or 25’. With a really long one, she stops before she really gets away, and then I can bend her and reel her in. Sometimes I’ve also experimented with a short rope and a lunge line attached as a backup.
I use a rope halter. I don’t like chains because they IME don’t release, or at least I have trouble getting them to release, but I also recognize that sometimes they are the right tool. There are some different kinds of rope halters too, and rope/nylon hybrids. Also the option of a lunging cavesson, though they are obnoxious to work with for ordinary halter activity.
I will also suggest wearing a helmet on the ground for a horse that pulls away. You don’t want your head to be suddenly and unexpectedly near any feet.