Dog won’t stop despite commands

I own a female 10y husky. My partner has a male pit/mastiff mix, just turned 1y.

Their dog met mine roughly around 5/6 months, he was adopted from a shelter and the shelter neutered him too young (some background info).

My husky has energy to rough house for some time, but eventually gets over it after while. My partner’s dog is relentless in play, hyper-fixated on when my dog moves (sometimes unprompted), doesn’t listen to my dog’s boundaries OR our correction measures, and bites/yanks at my dog’s neck.

I thought as a puppy he would learn when my dog corrected him for boundaries, but I feel like he only gets more activated and doesn’t stop. Sometimes even redirects “playful” biting on us with limited listening to commands to stop.

I just convinced my partner about kennel work, and has improved some behaviors. Bones/stimulation toys entertain for so long. Long walks/exercise only solves it for a minimal amount of time if we’re lucky. We’re consistently working on boundaries and recall. He can be very stubborn and defiant.

I want our dogs to co-exist peacefully, at times it’s overstimulating for us both, and I hate having to separate my own dog in her own space for her peace of mind and safety. It’s even worse when she cries cause she wants to be with us and it kills me. I want a behaviorist trainer, my partner doesn’t want to invest in expensive training. I’m at the point of there’s no choice.

I own a husky and trained a difficult, high energy breed since she was a puppy with her own behavioral issues from the jump. I have an idea of what I’m doing. But I feel tapped and out of ideas at this point. Obviously rehoming is not an option for either of us.

Is a behaviorist going to improve anything or is it just going to be consistent redirection and separation/“time-out time” for the remainder of her life?