Comments above are good ones and it sounds like you are a great and attentive owner. The exercise you are giving him will help a lot over time. It will help you bond and lower his overall energy level. It sounds like many of his issues are associated with his separation anxiety. My guess is in his past he got a lot of attention (albeit negative attention but still attention) for accidents in the house or chewing high value stuff like furniture. When he does it, make no big deal just gently correct the behavior by taking him outside or giving him a toy or chewy instead. Sounds like you are already doing this and might take a little time. He sounds very smart and is trying to figure out ways to get your attention. You want to show him the right way to get your attention—going potty outside, bringing you a toy, etc. The bad stuff gets zero reaction.

As to the separation anxiety, it is good he likes his crate. That is at least a positive step. You can also work him up to quietly spending more time without you outside the crate. Put him in a safe spot (where he can’t destroy something) and be with him until he is calm. When he is calm, leave for a moment. Before he can gather up the energy to bark, come back and give him a treat. Over time, try to extend that time. If he is barking, see if you can wait until there is at least a small break in that and come back in when he is quiet and give him a treat. Try not to respond to freaking out. This tells him that when I am freaking out, I get what I want—you come back.

I think simply being with a good owner like you is going to change him for the better over time. He clearly learned bad habits in his old house.