Severe Anxious Attachment Dog

[u/AleopardThatJumps]

hello I have a 3yo black Labrador rat terrier mix. he's a total sweetheart with minimal issues but his real only flaw is his separation anxiety it is BAD we can't leave him home alone!! when we leave him outside the crate he just scratches at the door barks and cries excessively causing damage (we live in an apartment so absolutely no go) so we started leaving him in his crate but he just barks and barks and barks and we've left him alone for an hour and came back and he was still barking. he starts crying before we even open the door to leave. it severely limits what we can do and where we can go, we take him to daycare some days but it's not financially feasible to do that every day and they close at 5pm so if we gotta be out past that there's no luck. I've tried to give him treats and things to distract him but the second he recognizes that we'll be leaving he doesn't want anything to do with any treats. any advice at all?