I think this will end up being too many fields in data. After looking at some of my previous report issues, I’ve had a very similar issue with the ARForm, which probably has the most tables and fields of any reports.
This has been previously posted about here: SSRS allowable maximum row size of 8060
@ckrusen mentioned a good approach in the above link. Copy your RDD and remove unused fields. Use the new copy to test.