Liz, you are doing the right thing in telling him it's okay to let go. You're giving him the peace of mind that he doesn't need to worry about you, and that whatever it is, you are there for each other in the end. They can continue to up the meds if he needs it but sitting in the garden with the beer and the sunshine works too.
My thoughts are with you both...and this completely sucks.
Regards JoAnne