The size of the batch should be a size that allows the process to complete in a minimal time during each iteration to avoid blocking other processes.  You could also...

Here is another option:

Declare @startDate date = '2018-01-01'
  , @endDate date = '2018-06-01';

 With reportDates
  As (
Select ReportDate = dateadd(month,...

You can rebuild the statistics with no_recompute - this will stop the statistics from being updated through auto update stats.  You will then have to insure the statistics are updated...