Not completely justified, but it's certainly understandable. It's reasonable that you're angry about his health condition and that he isn't improving, but ultimately it isn't his fault. It's a good idea to get those feelings out, but maybe don't direct them towards him.
Maybe he didn't go to the funeral because he didn't want people to see him sad? Hard to tell, different people handle grief differently.
You're probably frustrated that he is going through so many hard things in his life right now, so he can't be much of a positive force in yours. I think you are being a little selfish. His friend passed away and he is suffering from an illness. It sounds like he needs your support more than ever right now, and you are not interested in how much work or emotion that involves.
None of this behavior is justified. However, there must be a deeper reason behind it. An unresolved issue from the past? Poorly chanelleged frustration and grief from everything that's been happening? Something definitely needs to be sorted out on your end, and maybe it would be best if you go that alone for now. It's not fair to him for you to get upset at him for no good reason.