I must bow to the fact that I was wrong in my answer to the OP. After discussing this with another Senior member of my association and using a white board, he proved to me that I was wrong in my answer.
The BU will cover the pickoff
and take any play on R2 going to 3rd. The PU (who signaled that he was staying home) will drop back and watch the action at 1st and be available for obstruction and the pulled foot, should help be needed by the BU's request. PU will also turn and watch any subsequent action at 3rd and be prepared for R2 to round and come home. This is also in keeping with the CCA manual.
Again, my apologies....... I blew it!