The solution / solution workflow don't really make much sense to me so I stuck with creating 3 and 6 month moving averages by RM category as the question asks.
output example caused the workflow to be slow and frustrating. Was a little confused one the requirement and what the output file was showing it needed to look like. With that said, I still was able to give a running 3 & 6 month rolling avg. based on name and category.