SP, this was my concern for you all along, which I mentioned a few times: that, in being so (at least superficially) friendly and civil with each other, I felt like you and Mrs SP were artificially avoiding some of the bile that needed to come out, and that you were probably only pushing it further down the road, as it was going to come out SOMEHOW.
I would have rather you faced all of this, full-bore, early on, and gotten past it.
I think your wife still has a LOT of rage to deal with, and I'm afraid you're going to continue to see more episodes like the ones you've reported recently. Let's see, what did you always call them??? oh yeah -- the "batshit crazy" moments.
In any event, I don't know why you apologized -- I don't think you did anything wrong, at least the way you characterized the conversation. Buy her a $100 Sears gift card, and point her to the Craftsman dept. and call it a day.