Re: Can't get PSA to zero
If he's got rising PSA on Lupron, he's a good candidate for Zytiga (abiraterone) or, better still, Xtandi (enzalutamide). Insurance might cover it if his PSA has been rising. Those are potent anti-androgens he would take along with the Lupron. Also, he can try switching to Firmagon instead of Lupron. Probably not a bad idea to add in Proscar or Avodart. Different medications may work for different guys, and thank God, there are more choices now than ever before.
You're right that best results are achieved from getting his PSA as low as possible. Testosterone should ideally be below 20. Maybe ask his doctor to check his DHT level too.
Hormone therapy acts more against libido than against erectile function. But if he feels like it, that's great that he can still enjoy that.