I agree with everything "deserthorsewoman" said but, I can put yet another spin the situation:
I have 22 acres, more than enough space for four horses.
Third in the pecking order is nothing but a bully - he's been with me 16+ years and I can't tell you how many times I've come close to giving that agitating SOB a lead earring.
He has deviled both the Lead and Second-in-command horse when they have been sick.
He devils the begeezus out of the 4th in order horse and will pin that horse in a skinny minute and either bite or kick him, if he can get away with it.
I even went to the time and expense to open up a section below the paddock and put a second gate at the bottom end, so horse #4 could get away from the Bully.
Horse #4 absolutely is not a fighter - in the 6+ years he's been here, he has never shown one inth of a moment of agression or challenge against another horse.
^^^^that may be your horse.
So the BO kindly put in a second hay feeder and is bringing in another mare and filly? Sweet -- sounds like the main focus here is $$$$.
It appears the other horses are using your horse for a whipping post. Survival of the Fittest is still in the modern-day gene pool and they will have no conscience about beating him down until he can't stand up for himself.
Pretty soon your horse may start losing weight because they won't let him near the feeder - they will intentionally starve him out - I helped get a mare in that kind of situation. I took the videos.
You also run the risk of the horse developing ulcers from the stress of never knowing when he's going to get slammed. I doubt he even has the opportunity to lay down and rest.
If my Bully horse feels the need, he will charge my #4 horse when that horse is lying down to enjoy a good roll. Unless, I'm close on the 4-wheeler to give him some of his own medicine with the buggy whip.
I know it's more money and a further drive but given three kicks to the head, and big pieces of missing flesh, I would get my horse "the flock out of there" five minutes ago. JMHO