All three breeds that make him up, are dominant. He isn't mean, he's dominant. He needs a home where the owners are more dominant and know how to raise a pup like him. He has typical behavior for the breeds that he is.
With your (for a lack of a better word) temperament, he isn't the right dog for you. And with having a Pom, they are such little dogs. It would be better for you to get another little dog, not a large dog.
Don't keep a pup that doesn't fit you or your household. It will only get worse and he'll get to the point where he will be out of control. I would either give him back or find him a home.
In the mean time, the best way that I have stopped puppies from biting is to let them bite my hand, palm down and squeeze their lower jaw. You don't have to do this really hard, but put enough pressure where he wants to let go and pull away from you. Don't let him go right away. When you squeeze the lower jaw be sure that you have your thumb behind one canine tooth and your first finger behind the other one. It's a more sensitive area as there are small glands there, so squeezing him there it will put pressure on the glands. And he will let go. Don't yell at him, just look him in the eye. if he keeps biting and or growls while your doing this, squeeze harder. You may need to make him cry. Still don't let go right away. Give it a few seconds.
You will have to do this 2 or 3 times, and he should stop and not do it again.
I would also either keep him on a leash, or every time he starts
to stalk your Pom, flip him on his back, and hold him there till he stops fighting. Don't hold him down with both hands, you may have to hold on to a back leg just enough to keep him on his back. Too much pressure and too many hands will make him fight more. Don't say anything but look him in the eye. Only release him when he stops fighting and is relaxed. The more he relaxes the more you relax your grip. Be sure that your hand that you are holding him down with is on the side of his neck to under his head so he can't bite you.
Reward him for his good behavior. This doesn't mean to keep feeding him treats. Praise him with patting, give him a tiny treat or give him a toy and play with him. When he is on a leash, when you teach him something new, give him a little treat and be sure to praise him by petting him.
Hold him up side down in your arms a few times a day. (hold him like a baby) Don't squeeze him too hard, just hold him. As soon as he starts to relax, relax your grip. Keep him that way and as he relaxes, talk to him in a quiet tone and start to rub his belly. If he starts to struggle tighten your grip on him. And repeat the above. Once he is relaxed, then rub his legs and feet, his face, his belly. When ever he starts to struggle, repeat the above.
This is the way to gently dominate the puppy. You must be consistent!
Take him to obedience classes! You may find someone there that will want him or they can help you place him in a home.
Also, feed him adult food. Be sure there are no added sugars. The more grains the more carbohydrates, the carbs turn into sugar. Sugar makes them more hyper.
He is not a dog for small children. Too much stimulation for him.
Sorry for such a long post!