Hyperarousal in an adolescent pup

I have a 1 year old herding mix who is sweet as can be, but we are really struggling. He seems to struggle with hyperarousal and possibly a bit of anxiety.

Our current challenges:

– we live in an apartment in a busy city neighborhood

– puppy is easily overstimulated on walks (primarily crazy zoomies and leash biting). treat scatters don't seem to help at all. "sniffaris" aren't really an option – he's too busy scanning the environment to want to sniff. we can barely make it a block in the city before he's over threshold and we have to turn around. hikes on a long line outside of the city used to seem a bit better, but recently he'll get these frantic zoomies then too and becomes inconsolable, even after taking a break with a chew. also occurs in a quiet parks.

– we are working through car anxiety (has improved slightly). He takes Clonidine for longer rides which seems to help a tiny bit.

– puppy is close to or over threshold as soon as we leave my apartment – even if we play, train, or practice calm beforehand

– he some reactivity towards other dogs (he came from a puppy hoarding situation so is very excited around other dogs) and will lay down/refuse to move in hopes he'll get to say hi to the other dog. we've been practicing engage/disengage which does seem to be helping a bit

– I also have a cat which contributes to arousal/frustration at home (desperately wants to play at all times)

– about 2 weeks ago, puppy started excessively grooming (licking + chewing off fur). the vet assessed him and had no major concerns re: medical issues such as allergies. he's continuing to self groom excessively. seems it may be related to low stress/frustration tolerance

– he was going to daycare 1x a week for socialization/exercise but was recently overly nippy with another pup so we have paused for the time being

We've also completed a few dog training classes – one focused on calmness and focus and another basic skills class. It seemed like he was getting the hang of settling indoors at least up until a few weeks ago, and now he's always pacing, bored, and refuses to nap outside of the crate.

I'm worried puppy isn't getting enough physical exercise which I imagine is contributing to some – if not all – of our challenges. I give him tons of mental enrichment activities at home to try to at least tire him our mentally. I take him to a Sniffspot for off leash time once a week at least. I'd love to take him on more sniffy walks and hikes, but he's SO easily overstimulated by the world around him, that I'm not sure it does us much good to just continue putting him into these states where he's so overwhelmed. I'm currently reading "Fired Up, Frantic, and Freaked Out" and working with a private trainer in hopes of learning some more ways to help him. I'd rather not add more medication given he's SO young, but I feel like I'm at a loss and his quality of life is absolutely suffering.

Any advice? Thanks!!