So sorry to read this, I know how difficult separation anxiety is. We struggled with it and it was a nightmare. But I came home the other day and found my cocker sleeping in my bed. Even though it's been years since we had trouble with real separation anxiety, seing her so relaxed when home alone made me tear up. So thankfully there is hope
I do think however that the only fool proof way to get over it is to start over. Get a dog sitter or try to get help from friends or family. Because every time you have to leave the dog for an hour or any time period that triggers the anxiety you sabotage all the good training you've done. So for the next weeks or months I would advise to do all you can to make sure you only leave the dog for however long he can tolerate.
I had to start with just walking out the door and coming back in again immediately. It took us a long time to work up to minutes, and then some more time before we could even consider an hour or more. I used all the tools I could think of. Kong, DAP diffuser, radio, lights on, webcam connected to my phone, dog sitters. Everything helped a little bit, but the training takes time.
My dog has never been very comfortable home alone, but she did stop being scared with training. She went from scratching the door and howling to eating her kong and then snoozing near the door. I've always had to make sure I don't stress before I leave her alone. I had to change from someone who was always running late to someone who had things ready and could leave the house without a fuss.
I don't know if you wanted tips or just hope, so I guess this is a mix, sorry. But I know the feeling of being trapped in the house and constantly worrying about if it's ever going to get better. It did get better for us. And my dog is pretty neurotic (and so am I if I'm being honest
) so I'd say there is hope for everyone, hang in there!
Oh and btw, good idea to try without the crate! I moved houses when my dog struggled (for different reasons) and it helped with the separation anxiety training. Obviously not suggesting you move
But I think sometimes the space we leave them in can become a trigger and changing rooms can potentially be helpful.