Sitka has matured into a very handsome boy!
Go back and reread your thread about Sitka being bullied at the dog park (2017)! The majority on this forum then said to keep your dog away from these situations, and you listened. It was wrong then and it's wrong now! Unless of course your goal is to have a dog that needs to be "managed" the rest of his life!
Because you listened to them back then though, if you want your dog to be okay around other dogs, it'll take some work. He's matured and gained some confidence, but is still fearful of other dogs. Precisely because you chose not to let him work through it then, when he was younger. The absolute only way to get him over that now is to have him around other dogs, and guide him as to what is and is not appropriate behavior.
If he's bullying other dogs, buy him a muzzle! I saw this work well recently with a 3 yr old GSD male who was a bit of a bully, running up and biting other dogs in the hind quarters.
The idea is simple, expose him enough to having strange dogs around that it becomes a non-event. Might seem counter intuitive to you (and many others), but it works, I've seen it work miracles countless times!
Or go yet again with the, and majority, conventional wisdom that got you here in the first place...
If you do go back and reread your thread, pay particular attention to the behavior "predictions" of the people advising you to avoid other dogs, or allowing them to be pressured too much.
My dog has a CGC certificate, which she passed easily first try and without any classes. She's absolutely fine with any strange dog we meet anywhere, provided they are, and we go off-leash all the time at the river, the beach, and recently in dog parks all over in five states (so far, we're still on the road!)! And she's gone almost daily to a dog park since she was 6 months old, so there's that...
It's not the size of the dog in the fight, it's the size of the fight in the dog. Mark Twain