I'm glad you are seeing a counselor because you need someone who is safe to talk to and work through things w/o being judged.
I think it was a very good idea for him to live somewhere else when he comes home. The pattern was there and let's face it, you both were under a lot of stress and trying to keep the peace when both of you knew that tempers probably were simmering beneath the surface about everything that has gone down. So, you still work together and have dinner every so often. When you have dinner, keep off the relationship topic, find things outside of the "relationship" to talk about and eventually he might thaw out just a bit more.
As for the family portrait, I can understand why his family might not want to include you. After all, you are separated and heaven knows what he's told them, i.e., blood is thicker than water. It's just a picture and if you do find your way back to each other, another can be done at a later time. I know that this hurts right now, but let it go. Family can be really strange about separations/divorce because they don't know what to say or do and do not want to be in the middle of the situation.
I'm glad you wrote and advised him of what has been going on w/you. At least he does understand and has been supportive. That's a step in the right direction. I don't think you were being needy by telling him the truth of what's going on w/you. You were being honest and unless I missed something, you didn't ask him to help you out. He's trying to be a friend and show you some understanding and kindness right now.
At this time, I wouldn't read too much into his "sudden" change of heart. I would keep my expectations very low and treat him just as you would a friend. I do think he considers you a friend right now and who knows, this may be the step in the right direction.
For now, just go about your business. Allow him to come to you. Be sure to purchase some duct tape so that you won't be tempted to contact him again and hand out some hard truth darts about him. He doesn't want to hear it and will shut down on you.
Try to accept him for who he is and do not try to rush the process. Continue to work on you...that's what is important right now...YOU! Keep the focus on you. Okay?
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.