What should I do with my min pin

I have a 3 year old min pin. He growls and barks at everyone who comes to our house. If they pet him he gets attached to them and acts like they belong to him. He gets very upset and growls and barks when they leave. He growls and barks at EVERYONE who walks by our fenced yard. He barks and growls at me when I go upstairs and he can't follow (I have a gate up so my 1 yr old does not take the stairs by herself). He just freaks out about everything. I have to keep him separated from my 3 year old son because they get too rough with each other. He has nipped at him but it was because he was being provoked. He also tries to mount my son sometimes, which makes me mad. Some people are scared of my dog because of the way he behaves, so I usually don't have anyone over. I've considered getting rid of him but my husband does not think we need to. I have 2 kids, I'm pregnant, what to do with this poor dog?

He needs to be properly trained. Some dogs were bred to bark, such as hounds and guarding type dogs. However, getting a sporting dog is no guarantee against a barking problem. Almost all breeds have some tendency to engage in alarm barking, although there is a great variation among individuals.

Physical need - The dog is hot, cold, hungry, thirsty, or has to eliminate. Barking is the dog's way of requesting that you accommodate one of these needs.

Emotional need - The dog is bored, anxious, or excited. Barking can be a request for attention, or a compulsive behavior resulting from a frustrated need for social and mental stimulation. -- This sounds like him, he as a bit of separation anxiety --