for me at least, giving up dope (or restricting myself to 1-2x a month HONESTLY) has been a long, yo-yo process, where the peaks and troughs over time have been getting shallower and less deep.
There never was a single, definitive moment where I woke up one day and said "okay, I'm completely done with dope" and managed to stick to that. Instead, I just try my best everyday, and not try to beat myself up when I have a lapse in judgement, or when I just feel like visiting the Badlands.
I strongly suspect (and the research bears it out) that those of us who actually live through this and end up relatively stable do so in this same fashion. Whether it is with the assistant of maintenance meds or not.
OP your post contains a lot of hyperbolic language; "sin" "love of my life" etc. Our ignorant society encourages us to see our drug and our use in hyperbolically bad terms, which paradoxically encourages us to view it as the opposite ("love of my life") when it's working and feeling good. In order to survive and thrive (whether that means sobriety, controlled use, chipping, maintenance, etc) you really have to remove both God and Satan from the picture and just see heroin for what it is; a substance that activates some receptors. It is neither a supernatural horror nor your Savior...it's just a thing. It has good and bad and neutral qualities but is mostly what you make of it.
You're a great writer, with a great story, but if you really want to move on from dope then you'll need to stop investing in the Telenovela version of your relationship with it and start working on getting bored with it. As long it's remains a game of Russian Roulette in your mind (regardless of what the medical reality is), you will keep playing.
PS your heart trouble was caused by your use because it was an advanced complication of endocarditis, an infection in the heart caused directly by IV drug use. Look it up. I would recommend you look into alternative means of ingestion now and decide how you're going to do it if/when you relapse in a way that wont hurt your heart: intramuscular injection (with good hygiene and unused, correctly sized needles and syringes) or intranasal or anal suppository methods are all great HR alternatives, the latter two being much safer.