Anyone worked with behaviorists for separation anxiety?

What was your experience? I’m at my wit’s end with my just over six month old pup. Got him at four months and have tried EVERYTHING but he has no tolerance to build upon despite working on this every day for two months. Sometimes he’s okay for a few seconds or even thirty and then days like today he flips out before I even get to the door.

Not asking for separation anxiety tips (I have read/tried everything, yes he has everything he needs/tired out/stuff to entertain himself/etc.) but for experiences with behaviorists specifically. It’s a lot of money if they’re just gonna recommend Naismith or Overall. Or if two months is too short of a time to expect progress I guess that’s helpful to know but in a couple months he will HAVE to learn to exist on his own when I go back to the office.

I hate that he’s so stressed out which of course then stresses me out.