Aggressive dog, please tell me what I've done wrong

My dog has never had agression issues till we moved in with my boyfriend and his dog. His dog also has agression issues, but not with either of us or my dog.

My dog is a 3 year old Papillion
Here's what went down, please give constructive criticism

Ari asked Howell to get off the couch. He didn't move. Ari picked up Howell, Howell started growling. Ari started petting and cooing at Howell while holding him. Howell is growling and giving warning nips to ari. I come up, make eye contact and tell Howell to get off, he growls at me. I reach to the front of his collar, he starts biting my hand hard. I pull him from the front of his collar off the couch.
He goes and hides behind the couch. I come and sit infront of him, looking stern and making eye contact and tell him to lye down. He keeps looking down, to the side etc. He doesn't sit. Lie down. I stare at him for about 4 or 5 minutes till he lies down. I say good dog, give him a short pet on the head and walk away.
He tries to follow me on the couch, I tell him no. He walks away.

10 minutes later, he jumps up on the other couch. I tell him off. He doesn't move. I stare at him for about a minute. He doesn't move. I go to try and pick him up and he bites my hands hard. I grab his scruff so he can't bite me, pick him up with my other arm while still holding scruff, I put him in the crate. I keep the door open, tell him to go lie down and stare at him till he does. He does after a minute. I close the door and walk away.


So that just happened. He has started resource gaurding, being protective of me (starts growling if my boyfriend gets near me at all lol unless we start petting him) become very vocal barking at things outside. He mostly is fine unless someone is moving him from somewhere he wants to be, or taking something away from him.

Looking into a dog trainer and agression councelling but I'd love to hear feedback.i know I must not be doing something correctly or maybe consistent enough.

Thanks!