Congrats on all the activities! I hope some of them can become longterm interests. With regards to the WAH, I shared your tendancy to black-&-white thinking, expecting him to either care only/think only about the OW (with no affection left for me) or vice versa. Or, if he was in a being warm to me phase, I expected that meant he'd lose interest in the OW. When he decided he wanted to work on our marriage, I expected that meant he no longer had feelings for the OW, and would behave towards me as if we were beginning a relationship.
Of course, I was wrong on all counts. His depression meant he was acting from his emotions, not from a rational perspective, and as we know, emotions are constantly changing in their focus, intensity, etc. I only caused myself pain by assuming that things were more clear-cut than they were, and by trying to project his future behaviour from anything he did.
Whether your BF takes a whim to send you a Christmas present, or tells his friends you're the best girl he was ever with, or calls twice a day for a week--it's still just fleeting emotions ... until he's done enough work on himself to actually know what he wants and how to gain control of himself again.
You talked about having a "closure" conversation with him. I'd strongly advise against that--he wouldn't get out of it what you wanted him to, and you'd run the risk of feeling rejected/too vulnerable because you opened your heart to someone who can't really see your pain at this moment.
Do, however, have a closure ceremony for yourself. Write a long and explicit letter that you never send, or do a forgiveness program. (There are some excellent multi-step programs available on the internet, or you can work through one with your C.) It's a way of getting some control back into your life, of showing yourself that you are the most important person you know, and of affirming how you would like to be in a healthy, grown-up relationship.
You say you'd take him back if he wanted to, today. Would you really want to be with someone, again, who was still depressed and had not yet learned to be emotionally available? Despite what your dad says, he's NOT a great catch until he's grown past his current limitations.
