Hey Jack,
WELCOME...You've found a good place to sit down and stay awhile. There are folks here who help each other through pretty much anything. IMO you are suffering from situational depression. I'm certainly no doctor, but it is what it implies. You are suffering from several health stressors, which I certainly understand. It seems as though you are running a race, but new hurdles keep appearing. It's okay if you need a break...but don't quit Jack!
At 70, you are still a relatively young man. My older brother is approaching 70, and I certainly wouldn't want him to give up on life. He's having some issues with a hernia and needs additional back surgery. He has technically retired, but has remained active with referee jobs. He's feeling down, too, as he's not being feeling too perky either.
As to whether or not to pursue additional treatment for the cancer, I'm not sure anyone can really advise. It's such a personal decision. I think for me, I would consider quality of life issues such as 1.) What will the treatment be? 2.) How will that affect my overall health? 3.) What's the prognosis if you don't?
Have you logged in to the Prostate Cancer forum? Those guys are dealing with the same issues. Maybe they can be more helpful.
Meanwhile, please know that we care. You sound lonely and sad. I think the PC guys might have something to offer you, too=)
Dixie