Well what a quandary you are in!
Sometimes when I read about eccentric BO's, I think the ones I have known are not so bad...even though sometimes they made me question my sanity!
So, first IMO would be to just forget about all the drama. When the BO gives you unsolicited advice, just say "thank you I have a lot to think about" and walk away.
Second, if the horse is lame, take him to a vet for a workup. (I have no idea what a bodyworker is, so no advice there). Once the vet gives you instructions, then you inform the BO what the vet instructions are and that they must be followed.
As to the riding instructor issue, just load up you horse and take lessons off property with whomever you want. IMO it would be best not to share this information with the BO. Just say you are going on a ride with a friend, and leave it at that.
No drama is just that, no drama. I've never discussed my horse or training with a BO unless I was specifically asking their advice (which rarely happened).
I did have one BO become very insistent on the care of my mare before she foaled. He insisted she be stall boarded the last three months, which I reluctantly agreed to even though it meant more $$ than her just pasture boarding. Then he kept giving her his very fine stemmed hay. This was an issue because that mare did not drink much in the stall, and I didn't want her to colic. He insisted his hay was better than mine, and kept putting it in her stall at night. Since there was no way to change his mind, I didn't bother. I would wait until he went to the house, then remove the hay and parcel it out to the other horses. Then I put my own hay in her stall. He never knew I changed out the hay, so no drama
Bottom line, if you can't avoid/ignore the unwanted advice, then look for a new place to board. One has to protect the horse, as they are dependent on their owners.
But all these issues can be dealt with by not being dependent on the BO for anything but general care. My equine vet even has a farrier that can be booked, so that might be something else you can look into, finding your own farrier and traveling to them. Again, no need to share this info with the BO. Conversely if the horses are ok barefoot, then learn how to trim them yourself.
Keep the relationship with the BO purely professional, write short notes if you want to avoid conversations.
There is always a way to work around most idiosyncrasies and still maintain ones sanity...just do your own thing and avoid all the drama.