I agree, I think this is a huge step forward. I feel like, maybe because of the break, he's had time to process and think about things more deeply rather than just on a fight or flight level. I feel like this email made it clear that he doesn't want to lose you, and has realized that just because he was willing to take you back didn't mean you were willing to stay. I think this is really positive, and I really hope you both (him moreso) follow through with the work that's going to be required. Congrats on the break through!!