Have not read all the posts, but my personal opinion is that is way too young to wean and dont know why the foal would not be allowed in pasture with the stallion with it's mother. They all learn social skills this way and those hours that foal is away it is missing out on the nutrition that it should be getting from it's mother which is vital for good physical development and health. Not to mention the security at that age- it causes undo stress on the foal and the mare. I dont know why some folks treat Miniature horses like puppies or kittens and think that a few weeks old is ok to wean.
A study done a while back showed with big horses, that weaning too early caused social skill issues (such as agression) and issues later such as cribbing, weaving and other problems. Even when foals have others their own age to play with, they learn their social skills from their dam and the older horses.
If the stallion has the temperment that a foal cannot be left with it's dam for pasture breeding, I would have second thoughts about breeding for that temperment. If not enough room is a problem, then I would be hand breeding the mare and leave the foal with her, as nature intended.