7 month is old puppy still biting

My 7month Pit/Lab mix that I’ve had since he was about 3 months old is great most of the time but can often be a terror. At 3 months when I got him he was an intense chomped right out of the box. It was never aggressive biting but very intense and it was hard to spend time with him. Time outs would work sometimes but not really solve the issue. The biggest thing that has helped honestly has been getting him enrichment. He’s pretty great off leash and we go on hikes and he enjoys playing with other dogs at the dog park who are of similar energy level. After he was about 4 or 5 months old his biting got much better. Being consistent with getting him enrichment, training and commands with positive reinforcement, and providing chews toys that are strong enough for his pit jaws has helped a lot and he’s much better around the house. But he can still have some pretty intense fits from time to time and I’m getting a little worried cause we’re pushing the teething phase and he’s getting bigger. He’s only about 45lbs rn but he still hasn’t grown into his paws and I’m thinking he’ll probably keep developing until he’s about and be somewhere between 60 and 70 lbs. his fits will generally happen when he’s overtired but lately when we’re we’re leaving the dog park and I leash him he’ll bite me the whole way out the gate. He calms down pretty much as soon as we get in the car and I’ve sort of started to work around this by instead of leashing him and walking him out, using a treat to call him over to the gate and and leashing him there to 1. Create a positive association with leaving 2. Just make it a little easier for myself He won’t bite me after that on the walk to the car but there are times when I may need to just leash him and go. I tried to yesterday and it was the same story with the biting. I think I’m attributing some of this to leash frustration. We try to keep our walks shorter when on leash and that has help and when off leash I try to find areas with low foot traffic. Like there’s a trail by the river that we’ve walked for probably up to an hour in both directions. he stays near me and we don’t see other people. No biting either. But if we go on long walks on leash he gets frustrated and the fits start. I’ve also been noticing some separation anxiety behaviors. He’s been tearing up more things when I leave even though in the past he’s been good so we’ve had to start crating again when I’m not home. I left him in the car to go into the grocery store for a few minutes recently and he tore up my drivers seat. And this is something that I’ve done many times before without a problem. I live in an apartment with one other roommate and they’ve adjusted to each other, but recently I had to go home for the Christmas break and I noticed we were taking some behavioral steps back. Some key factors are 1. There were a lot more people in the house and he was constantly stimulated so it was harder to get him to be calm cause he was constantly excited by other people 2. There was another dog there. My parents have a much smaller dog, a 2 year old Yorkie terrier mix who’s mostly grown out of her all her puppy energy and was not really comfortable with a much bigger dog coming at her. He only wanted to play but he plays rough and scared her so he was spending a lot more time in the crate and becoming a lot more pushy with boundaries because he wasn’t getting the same level attention. 3. At my parents house he slept in the living room in his crate because my mom wouldn’t allow him in my bedroom. He will typically sleep on my bed at home so this was an adjustment for him 4. My family wasn’t use to having bigger dogs around and was a little warry of him giving him another reason to spend much more time crated

Since being back home things have settled a little more. I’m trying to be a little more active about his training because after I figured out that getting him excersize makes him calmer around the house we eased up a little bit because things were a little easier but in retrospect I think we weren’t doing as good of a job correcting behaviors as I should’ve been. What are some things I can do better? I can’t afford a behaviorist rn but I have one that I keep in contact with who my dog stayed with when I went on trip to Atlanta. I did a puppy training class at the rspca and he did well, but the class sizes were too large and it was hard to keep my dog focused and the trainer mostly focused on positive reinforcement and I felt like I wasn’t really learning to correct the behaviors that I was most concerned about. He’s getting better but I’m worried about these issues persisting past a year. Any advice?