I haven't met you, but your portfolio is very well done. Clearly photography has had something to offer you through the years, and I suggest you think twice before major changes. We all go through phases, where the camera doesn't offer the appeal that it once did. You've hit a rough patch, but that doesn't mean that your life is over. Sure, put the camera down for now, and focus on supporting your wife. However I do suggest that you leave your postings on the site, and maybe visit in a year or so. Old friends would certainly welcome you back. Also, photography might one day offer you a strange release of tension, if you spend a lot if time shuffling her off to cardiology visits.
Incidentally, you are clinically depressed. Obviously a situation has precipitated this, but depression may be a problem that your personal physician can help with. Copy the note that you typed for us here, and show it to your doc as an icebreaker. You might be surprised at what can be done, especially when you look back at this time from the distant future.