I'm glad that you had a decent talk with him. The animal hoarding concerns from his mother also should be addressed before she decides to do something about your animals without consulting you (or just consulting Sam...).
It just sounds like he has a controlling tendency to me from how you describe it. I have an issue with anyone who pokes their nose into my business as far as my snakes go, let alone someone who thinks they can decide that snakes in the collection gotta go. Downsizing when you need to for legitimate reasons is a good idea and makes it easier for you resource-wise. But that should be a decision YOU make, not him.
Not much more I can say, I'd had left him when he started having issues with the number of snakes in the first place. But I also went through a relationship where I was unhappy to the point of exploding for years, so red flag behavior makes me immediately disregard the person. Keep doing your snake thingWe know you aren't hoarding or crazy, and I'm pretty sure you'll be able to decide how much is too much for you. Good luck hon, it's your business and not his