I agree with most who say, you’re likely going to have to move. If BO has refused to make the alterations to keep your mare’s stall clean & dry to help with the skin condition, that is not likely to change. At the last barn I was at, we all had “our” stalls, but there would be a bit of float during the day when horses were being worked - the main aisle where the trainer worked - horses that were coming in to be worked or cooling down would get tossed in wherever if their “personal” stall was in a different wing - save for no one getting put in the stallion’s stall even if he was turned out at the time.
While I don’t 100% agree with the “you’re a guest” philosophy from some posters, I do understand the viewpoint. I am paying for use of the facility and if I am meeting the expectations of the boarding contract, I should be getting the services outlined. The BO is getting compensated, they are not housing my horse for free out of the goodness of their heart.
The only thing on your initial list that would be a deal breaker for me would be the shared stall situation if I was not made aware of that up front when signing the boarding contract.
If the farm was set up for pasture board to the point of the correct facing & size shelters in the fields for the pasture board horses - more horses than stalls would not necessarily be a deal-breaker for me.
I’d be on the fence about the underage afternoon feeders. I don’t know that I’d be super happy about no adults onsite at all while they were feeding, but it would also depend on whether you were talking about a 17 1/2 yo long term working student or a 14yo new lesson kid. Are they adding smartpak supplements or are there 15yo girls administering Regu-Mate?
At one barn I was at, the kid feeder was great - the 20-something barn manager, not so much… I had to go round and round with the BO over my “excess” smartpaks. The 20-something was supposed to feed supplements in the morning. I was almost a month ahead at one point. I finally got the point across when myself and several others with the same problem showed the BO the ship date on our smartpak accounts where they were getting shipped every 28 days ON.THE.DOT. We should have had at most a 7 day overlap.