Cobra,
Perhaps my view of the conversation is not as it actually happened. I don't think that your question was a boundary...boundaries are saying what YOU will tolerate, not trying to force an answer out of the other person. However, it may not have been an attack...it might have just sounded that way in print.

Here's how it appeared to me:
The Mrs brings up her need for an apology, you apologize for your contributions but you're feeling a bit cornered..a bit defensive and pissy that she's trying to pull this so the very next thing you say (after that convo is over) is your need for a marriage commitment. It smacks of "oh yeah, well take this" cause you knew that she would not be able to give it and it fulfilled a little bit of your need for payback, perhaps?

Oh well, it's certainly not worthy of this much discussion. I'm surprised that you can't see any room for improvement within your own behavior--only hers.
I can't count how many times I've thought back on my own situation and thought, Oh I got advice along those lines a while back..sure wish I would have listened to it then.
Other people seem to be able to see our situations more clearly than we do.

Best,
H.