Thanks for all the ideas and support
A bit more info on Comet for those who asked...
~he is coming 6 years old...has had lots of attention and time spent on him from us in the past year since we adopted him, not lots of training per se, but trust, relationship issues, and hoof care, as he was foundered--has thankfully grown in healthier hooves--and suffered from chronic abscesses
~he has never been ridden, don't know if that is a route we are going to take with him. I just can't picture him being ridden. He does seem a bit wild Donald. Like a horse that just wants to be left to be a horse.
~He is fairly high in the herd, but 2 mares and one older gelding are definitely above him. There are between 15- 20 horses usually in the pasture. The herd dynamics are different now that they mostly stick around the hay.
~He is often over-aggressive with the other horses, and possessive of me in the pasture
~I don't technically do any training in the pasture, just spend time with them out there when it's too cold to do anything else, like yesterday. Just pet/scratch each horse for about 10 min. then back into the warm car.
~several people around the barn have suggested he is a proud cut stallion because of his aggressive rearing, striking, posturing etc. and very active herding of the mares...but he never acts out sexually...even when pesky mares are in heat, he just turns his back and tries to stay away from them. When we first moved our 3 horses there, he kept all other horses away from his 2 fillies for quite a long time. he would charge, rear and strike, bite, kick out at anyone who tried to come near them.
~he used to be very herd bound, not wanting to leave the pasture, now he doesn't mind so much, but he will get worried if one of our girls is out of sight for too long. If they have been gone from the pasture for several hours he attacks them when they get back
he sticks to himself more these days, and just looks plain miserable
~he was previously neglected, very untrusting, completely dissociated and it took months for us to even be able to touch, handle him consistently
~he has never been very affectionate, doesn't like a lot of touching or brushing. will back up if he feels you're being too touchy
~he is the horse who always will go with you...ie, they are in a pasture that is at least 100 acres, and if you go for a walk across it he stays right at your shoulder, without a halter or anything.
~when Comet struck out I had taken a step back, so I was still facing him. It happened so fast, I can't really say even what his facial expression was like when he did it. I was thinking he was in a pretty good mood, and he had just really enjoyed having his face and eyes scratched, and the icicles picked off. He usually doesn't like a lot of rubbing on the face especially, but he was really itchy, and rubbing his face on my hands too. He seemed cute and foal like, a way he doesn't act very often.
~he does get possessive though, so maybe when he saw I was leaving he reacted to that with his leg. for whatever reason he did it though, it just isn't good. I am often out there alone, and have to feel safe enough to at least get him up into the arena.
~figuring out how to be with him is tough. he clearly dislikes any move you make to show him you are being dominant and pushy, and we worked so hard to earn his trust, it kind of defeats that. but at the same time, he has no trouble showing his dominance, and now acting out physically. I don't want him to become dangerous...well I suppose many people would say he already is dangerous.
on a side note, I suppose I also need to let the lady where we board about this. Everyone already stays away from him, and he doesn't like people he doesn't know just walking up to him. But she should be aware. I'm scared she'll say he can't stay there if he's acting out like that.