I think part of the reason he has been so unremorseful is because the A ended so long before he told you and the marriage continued just fine (in his head) anyway. In other words, he probably thinks the A didn't impact the marriage, only the confession did.
I agree with this and I think it's taken him all of these 9 months to finally realise that it wasn't the confession - but the affair, the selfishness, and the lying for 8 years that have really done the damage. It's not your knowledge but his own actions that caused the damage and it took him 9 months to see/accept that.
Also, if I remember correctly and haven't got you mixed up with someone else, didn't he and the OW carry on working in the same place, and still have 'some' kind of working contact with each other for all those years too? If that is correct (?) - then there was absolutely no consequences for him at all before you knew for sure - not at home, or at work.
When he was in the affair he wasn't thinking about anyone but himself - that's why he could lie to you on the phone so easily. I've no doubt he lied to the OW about what he was saying to you at the time as well. He was being as blinkered and selfish as all people in affairs usually are.
He didn't want to think about how any of this affected anyone but himself when he was having the affair, or at any time in all those 8 years since - and since [he wasn't badly affected by it, he could just ignore it and put it to the back of his mind. The longer it went on the easier I would imagine that got.
There just weren't any consequences for it. You didn't know about the A, so you hadn't been hurt (in his mind) and because you didn't know, he didn't have to implement a complete NC that might cause questions to be asked at work - so neither he nor the OW were adversely affected at work by it either.
Because of that, I think as time went by it was possible for him to start to believe that what he did was less and less damaging than it really was. Everyone just carried on the same - for all those years. Your marriage actually got better - and work was still comfortable.
He wasn't shamed at home or at work, and as time went on - and the OW and the A meant less and less to him, I think his guilt may have got less and less too. So when he finally did confess the A, he thought it would/should matter less to you too, because it mattered less to him. It was all over so long ago. (In his mind)
I think you had to force remorse out of him, because he was still only seeing this through his own eyes. He had had 8 long years to get used to it mattering less and less (to him).
The sheer depth of your hurt was probably a shock to him, and it's taken him this long since D-Day to realise and finally accept just how much damage he has done to you. To accept that there are going to be consequences that are REAL and long lasting to the both of you.
He is finally having to face and witness how much he has hurt you - that's why it's hitting him so hard and why he's finally got remorse imo. He's actually started to think about you after all this time. Before it was all him imo.
And in the back of my head is this little voice that will not shut-up asking HOW the heck I can reconcile with someone who did all that stuff and couldn't be bothered to even feel sorry...
Well, this may end up being too little too late for you - but I don't think he was someone anywhere near ready to R until he got to where he is now.
I hope things have improved a little for you today ((ItsaClimb))