Advice please: let him go or what!?

I met this guy on Instagram. Seems like a really nice guy and we started texting here and there. We are on the same page, want the same things, have a lot in common, etc... we seemed to hit it off pretty good.

Thing is, he has horrible depression because of some trauma he’s been through last year. So he tends to go silent and ignore me for days straight. He’ll go 3 days without texting, send me one text and then go silent again. It’s frustrating, but I’ve been very patient. Lately, it’s getting worse and he barely messages me. I was hoping to meet him and hopefully start something. I want this to go somewhere. He seems into me when he texts me, but if he was into me, I would think he’d message me more. What should I do?