Hi K.,
I don't have a whole lot of advice, but I can sort of relate. Although our decision to get a puppy was an agreement, it was poor timing. We had lost our boxer a year prior to cancer (he died less than 12 hours after we got the diagnosis) and decided to get a puppy. Well, a week AFTER we got the puppy, I got pregnant (also planned) . . .but had the worst morning sickness and ended up being on bed rest for a good portion of my pregnancy.
I was VERY resentful of the puppy and I felt awful and there were times that I threw the "you're the one who picked him out" phrase at my husband. If we did it over again, we definitely would have waited until a year after the baby was born, but we didn't and we're here now.
The puppy stage is ALWAYS hard, whether you are pregnant, with a new baby, or have no other obligations.
Maybe try to make the potty training "fun" for everyone . ..make it a game for your son and keeping Butkis from pooping and peeing on your carpet. Make it a game for EVERYONE to go outside and watch him to do it and give him lots of praise. I KNOW how awful that can be (its the only time I LOVED having all hardwood or ceramic in our house).
I don't have a whole lot of advice, because I don't feel like I handled our puppy stage with a whole lot of grace. I do know that the dog will begin to feel the resentment and that won't be fun to have to retrain his negative behaviors.
Be stern with the puppy about not nipping, I am sure there will be other advice here, but I just wanted to let you know that I have been in similar shoes. Put him on a leash at all times, so he can't jump.
Our boys are 4 and 1 now and the "puppy" is now 2 . . .they really get a long well together . . .all of them. I am not the biggest fan of our dog, but I love how the boys are able to rough house with him and the relationship that they have. I will tell you though, the dog knows that I am not his biggest fan and I am working on "repairing" that relationship, and its tough. Try not to show Butkis how much disdain you have for him (I KNOW its hard).
Hugs,
B.
p.s. he ran through my flowers last week . . .