Thank you so much!
I have one last issue, which is integrating him with our older and much smaller dog. She's a 3 year old Shih Tzu, but she was the runt of her liter and maxed out at 8 lbs. We think he thinks she's another puppy, not an adult dog, and he lunges at her to initiate play. He is only ever in a playpen or on a leash around the house/backyard, so thankfully he hasn't ever reached her with these lunges, but I still can't find anything helpful when it comes to that situation. He lunges at her regardless of situation, how tired he is, how distracted he is, how recently he was played with, etc. She never corrects him and just hunches down or runs away when he lunges.
Other than keeping them apart and trying to reassure the Shih Tzu that we won't let him get her, is there anything we can do to help them bond and stop the lunging? Will age eventually help? Or just more socialization with other dogs so he can learn to play gently?
Thank you again for answering, every day is a new challenge but also new wins!