Outsmart, I'm so sorry for your pain. Your wife is obviously totally brainwashed, but that does not excuse telling your own children you are Satan's friend! That is beyond disgusting and vile! How dare she? You are not a sperm donor, you are their FATHER!! And you need to stop the indoctrination as best as you can. A 3 y.o. should not be quoting a jw video. Please follow others advice and record your kids. An attorney would be the best one to tell you how to go about this. This may sound strange, but you may want to take cues from how Katie Holmes divorced Tom Cruise. Seems as though she moved stealth like, did her homework, had great legal advice, and made sure she had all her ducks in a row first.
So glad you are getting help for your depression. You should be feeling more like your old self in a bit. Just please don't share too much with your wife. It's none of her business.
It sounds as though some of the activities you enjoyed are ones your children may enjoy doing with you, biking, maybe hiking instead of running, perhaps soccer or throwing baseballs? I can imagine that if you talk to them about God, if you have beliefs, share with them. Let them know you are NOT satan's friend! You can let them see that Daddy is not what Mom is making him out to be without saying anything negative about her.
If you decide that the marriage is not salvagable, please go for 50% custody, so you can prevent total indoctrination.
I wish you all the best.