STRUGGLING with GSD PUP

I have a 3.5 month old rescue GSD (I suspect working line). I have done years of research on working breed dogs, specifically Dobermans before getting a dog and was approved and waiting for a match with a Doberman rescue when this sweet little guy fell in my lap and how could i say no😭 in hindsight, I picked the most difficult timing ever- I have a 3 year old daughter. I thought this would’ve been better than a newborn so we just waited for a really long time and I really felt it was a good time but it’s kicking my butt. He truly is a sweet sweet boy. We aren’t having issues fulfilling his energy requirements. We hike almost daily and play lots of games for enrichment with him as well but naturally my kid is struggling a bit with the adjustment as shes never had to share any attention and shes having a potty training regression so I already feel so guilty:( he is wonderful with potty training. My struggles with him are 1. The nipping omg I know this is normal but ive never had a dog who nipped like this. We redirect, yelp, all of it but hes just crazy with it. I feel so guilty for having such big feelings about it when it’s not even his fault but it almost sends me into a spiral when he does it to my daughter bc then the two of them are just so hard to handle together. Pls somebody tell me there’s an end in sight to this?!?! I can deal with all the other puppy behaviors but the nipping has me losing my mind. He seems to have made slight improvements with consistency of redirection but it’s still pretty intense fs. 2. Prey drive. Again- this is instinct. I know about this and I know it’s normal and not aggressive. But he gets excited and almost instinctual when my daughter runs or dances, etc. probably because she’s small and moving fast. Ik it’s prey drive bc he crouches down, the tail moves slowly and he pounces and barks not a playful puppy bark. Hes wonderful with her 100% of the time outside of this. Idk what hed do if I let him but during together play time hes always leashed because I don’t trust this instinct without a proper channel. Flirt pole was my next hope so I’m praying that helps.

We are working with a dog trainer who has been wonderful with potty and obedience bur doesn’t have much breed specific experience with working dogs and I do need help I think. We are signing him up on top of his normal training for training with a GSD k9 who trains working dogs and service animals. I’m really hoping he can help me with this prey drive. It’s not the quality itself I don’t want I just need him to know my daughter is off limits 100%. So far all Weve done for this is building trust and respect by having my daughter hand feed him meals as well as moving his crate to her bedroom to encourage bonding and controlled on leash exposures to her playing and what triggers his prey drive but treating him for neutral behavior. Any other tips? I need him safe around her 100% of the time.

Ugh I know I should’ve known after all this research but this is just SO hard. Tell me it gets easierrrrrrr