Any advice or comfort would be appreciated
Welcome to the Board. I'll keep my remarks brief.
One of the things you need to remember about drugs like heroin is they permanently alter the brain chemistry of the user. Addicts can successfully detox off heroin, but the brain remembers what it's like to be under the influence of it. What is it like? Bliss. No pain, no discomfort, just this feeling of warmth. When that feeling goes away, the user is desperate to get back to that place. And in order to get there, they will do
anything to get there: lie, cheat, steal, etc.
Your relationship with him never had a chance. It didn't matter what you said or did because addiction to heroin and other opiates is more powerful than love and the user's instinct to survive.
So, what to do? Allow yourself the time to heal. Step back, and look at your choices objectively. This will take some time and some hard work on your part. But if you're to learn from this, you really don't have a choice.
Keep us posted.