I like to watch all the dog training shows on tv and It’s Me Or The Dog did an interesting approach to the topic of seperation anxiety. If I recall she did a code word then would leave the dog for only a min or so (maybe even only in another room) and then with time increased the time and frequency away from the dog. Might be something to look into. I had a dog previously w/ seperation anxiety who required medications for a short period before adjusting to being crated when I would leave. Have you tried the Kong w/ peanut butter or frozen gravy inside of it to keep your dog busy? Before you leave the home are you tireing your dog out so maybe will have less energy to be destructive?
Raisin doesn’t have seperation anxiety but he is destructive esp when he bored so if you find any tips on other things to keep him busy please let me know. Good luck.