Looking back, you were T3N0M0 G4+5, which is a high risk diagnosis. It would be interesting to know what your PSA is now, but your PSA wasn't very high to start with, so that might not be a useful indication.
I think the thing to do would be to ask your oncologist what your chance of a cure is with 18 months HT versus 36 month HT.
What is important is to be having regular erections to preserve function. If you can't do that naturally, you should be doing it using Tadalafil and/or a pump, whatever works for you.
I'm sorry to tell you that from personal experience, stopping the HT doesn't magically make the weight fall off. Libido comes back when your Testosterone returns, which happens quite suddenly somewhere between 6-15 months after the last injection runs out.