I'm so sorry that you're having to deal with this..and long distance too
My husband is strong, but my depression wears him down at times, understandably. I feel like a drain on him and he needs to reassure me a lot.
I think the best thing you can do for both of you is to take care of your own needs. You can't help him if you are not happy and healthy.
I think he might be sabotaging your relationship without realizing it. People with depression have low self-esteem and don't see any worth in themselves. Telling you he's not worthy and making you miserable validates that. Like a self-fulfilling prophesy.
I wish I could help more. Is couples counseling an option in the future?