Dog with Generalized Anxiety "Globally Fearful"

We met with a behaviorist yesterday and boy I'm glad we booked the appointment a month ago. We got our border heeler at 11wks (sign said 8, kinda mad we missed that socialization period) from the 2nd shelter he had been in (not the nicest place either). He was in a shelter since 7wks. He's always been anxious for us. We were never able to crate him, he freaked out and escaped. We have an older dog who is not crated, so I think this only exacerbated the issue. He's fine left out, never been destructive. He's always been afraid of loud noises (thunderstorms, fireworks are to ne expected) but also new noises like trucks outside, snapping a paint stick...new stuff. Getting his harness on is a chore. Recently he wont walk or go in the front yard. The behaviorist describes him as globally fearful and having a bubble (honestly, hes the dog version of me). So, alas, she has recommended meds paired with behavior modification. He's never been aggressive or even growled with us or the dog. Until yesterday, the behaviorist knocked on a wall and he ran up to her and growled...going past the threshold quite quick. Today he growled at our other dog over a new food toy. I guess I'm just looking for stories from those who have been there and meds with training have helped. I have a message into the vet to discuss meds. Meeting with her was beneficial in learning his body language and that even taking a treat from us and us petting him there, he was nervous. I feel awful that we haven't done this sooner. Things have really escalted in the last month though. Just looking for some reassurance.