Keep the hope up, but SuperSize the Patience Patience Patience.
Your guy sounds like he is having some lucid moments. Doesn't mean he is anywhere near having a clear head. Still lots of little alien buggers in there you know.
But you are getting to hear a bit from the old H and that must be sweet. He is telling you little bits of stuff and doesn't even know why. He must feel quite comfortable in those moments, like before the end of the world.
You want him to remember the ease with which those talks go on. He will feel more relaxed and above all else "Safe" with your talks. He must feel safe to remember who you two were. He has not been safe for a long time because there were so many demons, so much guilt, and so much confusion. Like a child with the mother, he will just be looking forward to being comforted again by a familiar voice. It is a seed that will grow slow over time.
We can't know what it will grow into. We can't know how long it will take. We can see that you enjoy these moments of watching it begin to grow so don't rush. Think about how quickly babies grow up and then we wish we had more time with them. Be there for your boy and watch him grow strong and healthy in small steps.
Then remember to enjoy your life just the way it is after the contacts. Do not let him drag you back onto the roller coaster. It will weaken you and he will know it, as he takes two steps back in fear of what will happen next.