Yes, each and every time you two have had an exchange it sets you back. Don't ever feel yourself to "blame" for that. That's not helpful. What you're doing is normal, doesn't help you, but a normal response to a very abnormal situation.
Ideally he could own up to what he has done. Ideally he could make some sense. He can't do either of those things. It would no doubt help you if he could see what he did and truly apologize from the heart, but it's just not in him.
He is erratic at best.
If I had the exchange with him that you just did - ohhh we were wonderful and blah blah and then I said no, we can never be together! I would be furious. I don't think he's actually stringing you along so much as feeding his ego and being that erratic person. People who are ok in their thinking don't do things like that. Well maybe evil people do, I don't know, but his exchanges with you sound like the ramblings of a drunk to be honest. He hasn't changed, probably never will.
So, don't be too hard on yourself, I think you are further ahead in your healing than you think, but more time will help you feel more centered.
You've mentioned many times, when there has been n/c for a few days, how much better you feel and when there is contact how much worse you feel. It will just take some time now to get past this latest debacle.
I think the crux of this many times is that people (and I use "people" because I have seen this several times) had a person who was initially either sober or not so far down the path of alcoholism and they were close to them and could talk to them and felt connected to them on a pretty deep level. All of a sudden, or over years, that person evaporates. Everything is secondary to that bottle of alcohol. We think if we keep trying we can tap back in to "that person" we knew initially, or even a couple of years ago, but that part of them is so fully under wraps, it is unreachable. Might appear for moments (which makes a person hope) but then it's gone again.
It's a cruel situation. That is why it's so important to stay away from all that. That part of him is well and truly masked by alcohol.