HI Justin
As request type is up at header level you should not need line by line flat rule. It's been a while but if ou have to include the LINE_ITEM_KEY in the rule result for line item key you would have asterisk instead of ITEMNUM (I remember having to do that as I used the program in SPRO to generate the function, decision table and populate the header).
I recommend you have a go at configuring your decision table for Request Number scenarios and see how you go. It won't take that long to set up the config and test it out.
Regards
Colleen