Hi, did you have any luck at the vets?
I know it's been a few weeks since you posted but just wanted to pick up on your question about having an 'anxious extrovert' dog and add a few of our experiences with Marley, as I know it helped me to know I wasn't the only one struggling when things were really bad here!
We rehomed Marley from Dogs Trust just over 2 years ago when he was around a year old and after a few months he began to have episodes of aggression - growling, snarling, snapping, making weird whiny noises and a couple of bites. We had the Dogs Trust behaviourist out to see us and offer some advice. They came up with 2 main things: firstly, he's a guarder; secondly, that he's ambivalent, which sound a bit like anxious extrovert.
With the ambivalent thing he gets very excited, gets himself right in the middle of a situation and then realises that he's not at all comfortable with the position he's found himself in and lashes out. For example - jumping up at visitors that he doesn't know that well because he's excited and then not being happy when they interact with him. We've had to do a lot of watching and learning his body language and we've tried to teach him that it's OK to take himself away from a situation he's uncomfortable with and go off to his safe space in his crate (we're lucky that he was crate trained by his original owners). He gets ignored if he grumbles and time out in the kitchen if he snarls or snaps. He's getting much better at moving away when he's uncomfortable rather than reacting and we're getting much better at spotting when he's uncomfortable and asking him to move away before he has a chance to react.
He's 3 now and we still always have to give him time out to have a nap/settle down in his crate when we are staying with friends/relatives or if we have guests. If we don't, he doesn't choose to settle and relax on his own, so he gets over excited and over tired and more likely to react badly if he feels uncomfortable.
In terms of touch, he hates being groomed with a passion. I chose to muzzle train him for this reason and he now wears a basket muzzle when he gets brushed, trimmed, bathed, and when he sees the vet (plus squeezy cheese to keep him standing still). I often carry both muzzle and cheese with me if we are going anywhere unfamiliar just in case, particularly when he won't have the option of taking himself to his crate, although I rarely need to use it.
For touch desensitisation, we were recommended the bucket game (google 'the bucket game for dogs'), which is all about the dog choosing to participate in the interaction. When we initially tried this, I didn't have much luck (hence using a muzzle and oodles of squeezy cheese) but I've since read 'When pigs fly' by Jane Killion and I might give it another go now I've got a better understanding of shaping behaviours.
Hoping you've had a smoother ride over the last few weeks!