Help my dog can't be a lone

[Oliver123]

I adopted a Daschund/Terrier mix about 5 months ago (he is 1 yr. old). When I first got him he showed minor signs of abandonment, but he was okay as long as he was not crated. However, about one month ago, I took him to stay with my father while I went on vacation and he went crazy. He chewed a hole in the screen window and jumped out when left out, then he chewed through an airline approved crate when crated, and either jumps over or chews through a gate when confined. The behavior continued once I returned. I have tried several things such as calming scents, calming gel and excessive exercising, but he still freaks out when left alone. Does anyone have any suggestions about how to work with my dog on his abandonment issues. I am willing to put in the work, but I have limited funds, so I would like to try to do as much work as I can myself before hiring a trainer.