Allocating an adjustment amount to previous event, then billing the amended amount, not the event am

We made an amendment

I believe my culprit to the above situation is that we did not uncheck Adjust Prior Billing and Adjust Prior Revenue - in that it's now trying to produce a bill for the difference in the previous event and the amended amount.  So my questions:  How can I undo this - can I delete the worksheet, then produce a negative event for the opposite to net to zero change?  Will it pick that event up with adjustment bill

When the Bill Plan is in Action Required, (because of this amendment, I presume) what can I do at that point to undo it?  I can't delete the completed event that has the amendment amount on it, so what is the recommended fixif you catch it at that point?