Hello! You and your dog may benefit from some classes. Training classes aren't just for pups! And you'll learn more than just training plus you'll have fellow dog owners to talk to. You can check with your local shelter for referals. Since you are new to this and choose an adult dog you may find a professional's opinion helpful - especially in a class setting where she/he knows you and your dog personally.
The big thing you have working in your favor is that he loves you and although at times it's hard to believe, he wants to make you happy.
To answer your last string of q's - you probably do have new mom jitters, yes it does get better over time with work, I don't know how long, and imo it is worth it. After a long day of chaos with my babes (2 human, 1 canine) it's all worth it when I see them snuggled up together as if nothing ever happened!
You are doing your best. Hang in there.
