Power Query Append Repeatability Issue

I have a raw data source that has 350K rows. Each month around 25K-30K new lines are added. I have two tables of an old mapping and new (tables in G:H and J:K). I must show the result in a pivot (M:Q) and have my results but not sure how to make repeatable. 

Here's my process I hope to make simpler and repeatable:

1) Two different workbooks I dump the raw data. Each workbook has either old or new mapping.

2) New workbook: I use Power Query to import the data from both workbooks then append the two together and output into a table.

3) Second new workbook: Use Power Query and create connection only to the workbook in step 2 then output my desired results in the Pivot.

My questions are: 

1) Am I doing this right? Can I need to be able to do the analysis I did in my example but not sure if I can do the same in one workbook rather than two for the old vs new lookups.

2) Can my process be improved? Can this be improved using Access rather than Excel? I need to improve processing as to setup (steps 1-3) took 1 hour alone for Power Query to process and then to refresh twice a month.