You may also use the operator form of Merge which compacts the Dataset query a bit.

myds[Merge[Min], 
 {"Reinsurance Payment Amount (or Not Eligible)", "Individual Market Risk Adjustment Transfer Amount"}]

Hope this helps.

Also, this seems to work:

myds[Min, #] & /@ {"Reinsurance Payment Amount (or Not Eligible)", 
  "Individual Market Risk Adjustment Transfer Amount"}

By this I mean that it gives the minimum of the 2 columns specified, equivalently

Map[myds[Min, #] &, {"Reinsurance Payment Amount (or Not Eligible)", 
  "Individual Market Risk Adjustment Transfer Amount"}]

HTH.