Dear Bizzy
SH** HAPPENS. No one knows that better than you because you have been buried under it on at least two occasions. Over the last year you have been on a real roller coaster with your partner but what has been changing is not the news, which has been consistently bad, but whether blame should be assigned to you or your partner. You are beating yourself up unnecessarily Bizzy. There is no blame to assign. These are not ordinary circumstances. You are both having crap flung at you from all directions. There is no prescribed way to behave and whatever you do is understandable. You are not guilty of anything. It is what it is.
As for the trip to Arizona, I don't think it was a bad idea.That it turned out badly is not surprising given your partner's condition. But he wanted to go to a beautiful place and see a close friend before he died. That's reasonable. If you hadn't gone you'd probably be second guessing yourself forever. And I think you shouldn't dwell on what your partner's friend thought. He was probably overwhelmed by your partner's appearance and lost perception of everything else. I think it was the trip itself rather than the friend that defined and affirmed the situation. You took the trip because it was the right thing to do and although you knew there could be complications around every corner it turned out to be a mess THROUGH NO FAULT OF YOUR OWN.
I agree with NatR that you need help. However I think that if you love your partner and can care for him without doing irreparable harm to yourself than you should continue caring for him. If one of the above doesn't hold then I think you are justified in withdrawing from your partner. In any case, even if your partner never again expresses his love and/or gratitude to you, have no doubt that you have been of immense help to him and he was very fortunate to have you in his life. Above all else - DON'T BEAT YOURSELF UP.
Tian