Rescue came home 3 weeks ago and still cries for hours when I leave - at what point do I give up on the crate?

So I adopted Biscuit 3 weeks ago from a local shelter. He's a 4 year old sheltie mix and honestly the sweetest dog I've ever met when I'm home. The second I leave though, my neighbor texted me yesterday saying she could hear crying through the walls for almost 2 hours straight.

I've been doing the crate thing because everything I read says it helps with separation anxiety, but i honestly cant tell if its helping or making it worse. I have a DAP diffuser running, I leave a shirt that smells like me in there, give him a frozen kong when I leave. He still just cries until he tires himself out apparently.

How long did it take your rescue to adjust? I dont want to give up too soon but i also feel terrible leaving him every day for work. Has anyone had success with anti-anxiety meds for this? My vet mentioned trazodone as an option.