I'm glad I read this, Phil. The way you are handling the squat reset, if I'm getting this right, is actually counterproductive.
First thing is you actually set it back a little too far but you can work with 160. 170 would have been better. But regardless of that microsetting back up is is no-no. You wan't you're body to recover and "catch up", yes, but due to the frequency it is easy to go too far and turn that in to detraining. In other words it is possible to drop the intensity low enough and for a long enough period that you are actually losing strength rather than just doing a back-off.
Basically, the back off should constitute building back up to the weight your plateaued at in around 3 workouts with the 4th workout being the new higher weight over and above that. If after a backoff like that you can't contiunue to progress by any means then you've probably done all you could with backing off.
The way your doing it now is overkill and your going to be spinning your wheels and playing catchup rather than just recovering from a plateau. I'd suggest that you add enough weight on your next few squats to where you'll hit the 187 again within 3 workouts. Then see if you can go to 189 or 190 (if not more).
I hope this makes sense