Separation anxiety in dog

I’m sorry, this is going to be super long but I’m a bit desperate.

My dog was essentially a stray before I took her in. She was passed around between multiple homes and everyone got to the point of saying “I’m going to put her down.” Finally, she made her way to me. She developed severe separation anxiety. I’ve been trying to work on this as much as I can but I’m struggling. Unfortunately, I’m not able to stay home all the time. I try to limit how much time I spend away from her but I have to leave the house sometimes, especially since I live alone. I have tried multiple things at this point. She has potty accidents, tears into the trash, etc. when I don’t crate her. With the crate, she tears the blanket off when I cover it with one. She destroys the plastic crate tray or the beds when I put those in there. She ignores her toys when I put those in there in favor of destroying anything else she can get ahold of. I give her calming treats or calming pupsicle but it’s like they don’t take effect until after I come home. She will pass out immediately after I get home and let her out. She’s a hunting breed of some sort, but I haven’t done a DNA test so best guess is a pointer. She has various “thinking toys” and recently got a “thinking” food bowl that she is still learning how to use. She goes on 2 walks a day but we live in a cold state and she is visibly shivering even with a sweater and jacket on. She also has been trained to use the treadmill to exert excess energy so I’ve been using that more lately. It does seem to be worse in the afternoon rather than the morning. For example, if I leave first thing in the morning then she does better than if I leave in the afternoon/evening. Google is saying that’s due to excess energy but I have tried to walk her or play with her right before I leave and I still see the same issues. I also have another dog, but he is fine with being left home alone. I’ve tried crating him, within view or out of view. I’ve left him free to roam, etc. Nothing regarding him seems to have an effect on her behavior.

Does anyone have any suggestions that I could try to help reduce her separation anxiety? I feel guilty going grocery shopping at this point, let alone to work or anything where I can’t bring them with me. I’m genuinely out of ideas and Google isn’t helping much anymore.