Hi,
Issue one - if you one only one line of Cost of tax ant to be static, you have to put it in the header. In fact, this is the way to make static table. You can pus as many as you want header line. But s long as you have the line where is the data, you will see many lines (as many as they are in the result of your dataset). If you don't want to see them, delete the line.

Issue No 2
=sum(iif(Fields!RevisionNumber.value = 2 and Fields!Status.value = 3 and Fields!ShipMethodID.value = 4,Fields!TaxAmt,0))

in your iif you have (condition, true, false)
if you need more than one condition you have to add and/or between them.
Also you have open ( with sum and second ( with iif but closed only once.

Good luck