To me, her bag looks like it is trying to dry up. One that is about to foal starts to look pretty full. Also the milk would look more of a golden color instead of white, because it would be colostrum. Most likely she had a foal already and it was weaned off before they took her to the sale. She would also be really showing by now if she was milking that much, and from the picture, she really doesn't appear to be in foal. Signs of foaling are a full bag, waxing of the teats, or dripping colostrum , Loose muscles on both sides close to her tail, and a loose vulva. I am 95% sure that she had a foal before you bought her. But I would keep a close eye on her anyway, since you really do not know.
As far as the kicking goes, that is pretty normal during feeding time, esp with an alpha mare. She is just showing him who is boss. I like to separate mine during feeding time, so no one gets hurt, or has to fight for food.
She is super cute, I LOVE minis, they are awesome!!!!