Maybe letting go IS still trying, in this case? In other words, it looks like what you may have top do both for yourself and this relationship is let it go.
You have to let go of this person per the level of detachment they have requested, no matter what: they're not talking to you, and have said they don't want to, so obviously you need to respect that. But I also think that maybe some of the work that might need to be done here -- some of what "trying" might look like in this situation -- is letting go of anyone who not only asks you to, but who also isn't showing you that it's healthy for you to hold on to them in the first place.
For sure, people can have some rough reactions when a partner discloses. But I think it's safe to say that people with the kind of emotional maturity and personal responsibility any of us need for a healthy partnership, let alone when we have an extra-big struggle in the mix, like a battle with a major and serious illness, will take ownership when they do react badly pretty soon. For example, this person could have just dropped you one more text that said, "I still don't want to have a relationship anymore, but I'm sorry I reacted the way I did to your diagnosis, which much be really hard for you. I hope that you can stay well and get through this, and I wish you the best," or something, you know? Instead, he left a sick person already struggling with an illness and situation that can be super-isolating feeling even more isolated. He made this about him. It also sounds like he's blaming you for his choices (like in the event he chose to have unprotected sex with you), which is really crappy.
Maybe "trying" in this case is trying for YOURSELF more than a relationship? Know what I mean?
Never doubt that a small group of thoughtful, committed citizens can change the world. Indeed, it is the only thing that ever has. - Margaret Mead