Maybe filling up the area behind the seal via the drain slot near the gasket break? Or going out the pan gasket?
Gotta wonder if the pump was jacked up just a tiny bit by the cap bolt and that allowed the gasket to let go. That cap bolt has a washer under it that will raise the bolt head. If there is contact to the pump body, any gap will worse with the gasket removed. Seems like this washer issue has reared its ugly head for others....
The gasket area around the lower right bolt in the pix looks messed with.... was that just from removing the pump? BTW, I'll always put a super thin skim coat of #2 Permatex on gaskets like that to make sure they stay put.
I'd still pull the rear cap and replace the seal, and investigate all of that.
