groin pull protocol....form and depth

Mr Rippetoe,
Tuesday, on my last set of 270, I was struggling. I should have racked it after the 4th rep. I was moving in slow motion and my form was degenerating. So of course I took a few extra breaths and tried to get my last rep. On the way down I felt a tweak in my groin....I made it about 4 inches up and felt a sharp pain in my right upper thigh, toward the rear. Adductor I believe. I set the weight on the spotter arms and rolled out from under it This morning (saturday) I did 3 sets of 20 body weight squats with a close stance ( about 12 inches apart) to make sure I could tolerate it. This evening I started the Bill Starr protocol. 20reps@45, 20@55, 20@65. It is hard to hit depth.Hurt my knees as well with was probably good because that helped take my mind off the uncomfortable warm feeling in the adductor. As the weight increases I am sure it will become more difficult to do this with a closed stance. Do I just keep going and open my stance only when I absolutely have to?

Thanks.

Adjust the stance to remain on the edge of your ability to tolerate it, until you're back to a normal stance.

Thank you.