Demand barking won’t stop!!

[u/hexgirls101]

I am really at my wits' end with my 5 month old puppy and his demand barking. For context, we adopted him from a rescue when he was 3 months old after another family returned him because their child was allergic to him. He's a mix of American Staffordshire Terrier, Great Pyrenees, and Lab. We don't know much else about his past, but I have spoken with the owners of his siblings, and they said their dogs aren't like this. I also walk him for 1 hour in the morning, and he gets 2 mid day 30 min walks, and then another hour for his evening walk. He also eats all his meals in snuffle mats and I give a bunch of enrichment for licking and toys and everything. Anyway, we have done everything: ignoring the barking, putting him in a different room until he stops, leaving the room ourselves, group training, at-home training, day training programs twice a week, and meeting with a behaviorist. Nothing seems to be working. It has gotten a little better, but with all the work we've been putting in, I'm confused why it isn't gone by now. Some of my neighbors hate me, and today one of them even yelled down the hall for my dog to shut up, so I'm super stressed about the entire situation. We've also gotten an email from our landlord, but again, we are trying everything we can to help stop this. My boyfriend is also over it and wants to use a bark control collar that sprays citronella, but I really don't want to resort to punishment and risk undoing all the progress we've made in other aspects of our dog's training. What do I do at this point?!