Newly adopted dog with separation anxiety

I want to preface by saying that I need honesty but kindness right now. I am in the very first few days of a newly adopted dog and am feeling all of the “puppy blues.” This is really hard and I’m trying my best.

On Saturday, I adopted a new dog from my local shelter. Male, -50ish pounds, 3yo lab mix. As sweet and affectionate as can be. Everything has been going great, but he is very attached to me and has serious separation anxiety. Whines, paces, pees, poops and never settles when left alone. He knows how to break out of a wire crate and turn doorknobs which is making me incredibly nervous for his safety in my home. I live alone and am managing this new dog by myself. I simply have to be able to leave him for a few hours a day for work and errands. I know what you’re going to say: he can’t tolerate that right now and I need to work up to his alone time in small increments. Though I would love to do that, I don’t currently have the luxury of doing so. I do not think I would have adopted him if I knew his separation anxiety was this bad. Being able to be safely left alone for a while is really important for my lifestyle. We’re going to the vet tomorrow and I suspect they’ll give meds to help with the anxiety. My own emotional state is wrecked right now.

Am I just feeling the overwhelm of the first few days of a new dog? Is it too soon to tell how big of an issue this is? Is this something we can work through? Or am I dealing with a real issue where I need to consider the possibility that this isn’t the right dog for me? In every other aspect, he seems like a great fit.

EDIT: I have done Kongs, lick mats, calming music etc. He did better in a “dog safe” closed off room than he did in the crate, but I’m still nervous because he knows how to open the door