I think I've suggested similar tactics on threads of yours before, but I think you and your DH would really benefit from both of you having some sort of stock phrase that you always use to respond to your MIL. It gives you time to check in with each other and see if what she's saying is outrageous-bad, outrageous-you-can-live-with-it, or actually not outrageous. And if you respond more or less the same way every time, you don't give her the same opening for the PA digs. Because you always respond this way, whether it's good, bad, or indifferent.
It's basically the same idea as what Toots suggested. From what I can see (based on the threads you've posted over the years), your MIL sticks her nose in to a lot of things in your life and your marriage. You don't always mind, it's not always worth fighting over, but she's always there. You and your DH frequently don't have any time or space to check in with each other because your MIL keeps herself so firmly between the two of you, and it results in a lot of misunderstanding and, at least on your end, frustration and hurt feelings. If you and your DH both start responding to your MIL with words but no real meaning, you'll shove her out of that space in between the two of you without ever having to have a big show-down.
And in the end, it's really not all that different a way of reacting as what your DH already does. It is, in essence, ignoring your MIL. You say something just agreeable enough that she feels that you have listened and responded, and she doesn't feel like she needs to argue, and then you go off and do whatever it is you were going to do in the first place.