Hi, this id Dr. Gabby.
I use Depo on horses for calming behavior. Those who spook and buck a lot. I normally only give it once a month. My average dose is 1000 mg which is 5 cc of the 200 mg per ml strength. I have never had to give it every week though. I charge $40 per injection.
The estrone is usually used for luxating patellas or in cases where the patella ligaments are weak. That means on downward transitions, especially from canter to trot, the patella ligaments may catch the patella and it feels like the hind end drops for a second. Normally you can strengthen the patella ligaments with hills, trot polls, backing, and transitions. So I am not as worried about the estrone as I think you could probably get him off it with work.
Neither drug is suppose to have long term effects although there are no studies and the use is "off label."
I would be annoyed if he needs depo every week. It would have been nice if the seller let you know about those injections but I can not really say if the seller should have told you.
I would call the seller and ask why they are giving the depo and estrone and see what they say.
It sounds like you own him now and can work with it.
Does that help? Do you have any additional questions?