To answer your questions, as you posed them.

1 - You can not use an 8 speed cassette with a 9 speed shifter. The amount that the 9 speed shifter will move the rear derailleur and the cassette spacing do not match. You need a 9 speed cassette to go with the shifter that you have. NOTE: You seem to misunderstand the cable pull issue. The shifter is the thing that determines the amount of cable pulled per shift. As you noted, the amounts are different between 8 and 9 speed. The smaller amount of cable pulled by the 9 speed shifter, causes the derailleur to move a smaller amount to match the 9 speed cassette spacing.

2 - There is no trick to making that Microshift(or any Shimano compatible) 8/9 speed rear derailleur work with either 8 or 9 speed shifters. Just hook up the cable in the normal fashion and the shifter will determine the number of cogs it will shift, by the amount of cable pulled.