Charlotte! Lovely to see you back here! (Not lovely, in the sense of glad you have to be back... you know what I mean) Have a 
There are good things to take from your time away - as you say, if things are better than ever, and the DCs are benefiting, that's a positive for you all. However, at the absolute end of all this is:
It doesn't really matter whether he's abusive, whether he continues to be, whether he would win father of the year awards, whether other people think you should give it another go.
All that matters is you, how you feel about him, whether you genuinely still want to be in a relationship with him.
If you do, then these changes are all positive, and you can monitor them as you say and see how things go when you start challenging his behaviours in the future.
If you don't still want to be married to him, if you feel that you can't get past all the things he's said and done in the past (which is perfectly understandable, and you are under no obligation to forgive and forget) then please take time now that you are back and think about that.
I agree, Matchsticks, I think I'd end up in the same situation with my FW, even though I left nearly a year ago. 
I wanted to share this link that I saw somewhere else, sure some of you have seen it but I thought it was pretty good. www.abuseandrelationships.org/
As a certain fluttery-one noted, this quote from the homepage is particularly good, I think:
Abuse is a twisted way to get needs met, but the twist toward limiting the other person's options is exactly where the destructiveness comes from.
I am sure Maggie was mostly posting on her phone before... doesn't that mean that she wouldn't have to have specific broadband account access to do that? (Not entirely sure about these things.)
Am wishing now that we'd asked her to PM one of us her mobile. Hope she's ok.