In D2

=SUMPRODUCT((Sales!$D$2:$D$15=Summary!A2)*(Sales!$I$2:$I$15))

in I2 of "Sales" (was in column J)

=SUMPRODUCT((Compensation!$D$2:$D$169)*(Compensation!$A$2:$A$169=$A2)*(Compensation!$B$2:$B$169>=Summary!$K$1)*(Compensation!$B$2:$B$169<=EOMONTH(Summary!$K$1,0)))

this will correct the formula.

Second, the "helper" column(s) can be in a separate sheet: I cannot find a way to do this without "helper" column(s) BUT I'll leave it to the other experts to look at..

However, with 15000 rows, then the [potential] use of array formulae (as a solution) will adversely impact on performance so do not dismiss using "helper" columns.