Poodle tearing up his back left paw, not so sure its allergies anymore?

Okay we have been treating my poodle for allergies (and other problems) his whole life. We had to totally change his diet due to gastrointestinal problems. His allergies have never been skin allergies, he has respiratory allergies and he is allergic to grass, pollen, dust, and other common allergens (poor thing). He does not have any food allergies (though he doesn't tolerate corn at all, so we don't feed anything will fillers such as corn, didn't learn that from allergy testing ofcourse, just process of elimination.). He has been through allergy testing.

One thing that he has been doing for quite some time is biting his back left paw. The vet has given us sprays and other medications for it, but he keeps biting his back paw.

Its to the point he is starting to tear up the pad.

I don't have a picture of the pad but her is a picture of the front of his back paw, and the red you see in it, well that is blood stain in his fur, where he has chewed it until it has bled. We came back one day after being gone and noticed that. And the staining won't come out.

Here is the photo:




Now I thought it was allergies at first but now I am not so sure. I mean for the most part his allergies are under control. I thought back to a previous dog I had and whenever that dog would get nervous or upset about something, he would chew and scratch sores into his skin.

The times I catch my poodle biting his paw (and I get onto him about it every time I catch him) is when we are getting ready to leave, you know getting dressed and getting ready to go. When he ends up in a situation where he is uncomfortable. If he gets scolded (my grandfather scolded him the other day when we were visiting).
And the worst I have ever seen his foot look is when we were gone with our other dog and he was left home alone for about 3 hours.

I think he is doing it when he gets nervous?

But how do I fix that? He is already being treated for anxiety and we are working on that.

He has nothing to be stressed about, we give him plenty of exercise (probably more than he even needs), plenty of play time, he is rarely left along. If we leave our other dog is home with him. I never leave him more than 3 hours at a time (normally he is left alone maybe an hour a day). He has lots of toys.

He has been high strung and nervous since the night we brought him home when he was a 9 week old puppy. (Vet said genetics could be part of why he is so nervous, because he has such a good life, and you can ask anyone who knows us and him. He couldn't be more loved and cared for and he couldn't have a better life. He has never been abandoned, neglected, or abused either before we got him. We got him when he was 9 weeks old but he is very badly bred and does have some genetic health issues, vet is really starting to think the anxiety is genetic. I remember his mother and aunt, they were both very high strung dogs, seemed kind of nervous. So I'll buy it)

Anyways what can I do to stop him from biting at this paw. He has a check up after Christmas so we will discuss this with the vet again.

It just bothers me because I knew another dog that did this and the foot got infected and it ended up amputated. I don't want that to happen to him.