Using the vacuum pump is not a test, but a procedure to bleed the air out of the clutch system. It's a much more reliable way for this procedure as you can do it your self and it's far more effective than having someone inside on the clutch and you opening and closing the bleed nipple at the right times. If you buy the vacuum pump there are instructions in there on how to use it or your mechanic should have one and he can do it for you.
The pressure plate is not a adjustable or any of the components inside the bell-housing. The only adjustment is the rod from the pedal to the master cylinder or on the slave cylinder itself, but most hydraulic slave cylinders are not adjustable, the only adjustment being in the master cylinder where it connects to the pedal. That's under the dash and it will be a bit awkward to get at, but not impossible.
Unlikely it will be a selector issue. If the trans. sat around outside in the wrecking yard for a time some moisture may have made its way in there causing the selectors to become sticky, but a transmission is designed to use the oil in itself to lubricate the forks, the selectors and the selector shafts.
When bleeding, make sure to keep the reservoir in the master cylinder topped up so that no air gets into the system. I am telling you this because you don't seam to quite understand what is going on here.
DOT 3 or 4 is fine, they are all interchangeable, even the synthetic stuff. They are all alcohol based products and are hydroscopic. (absorb water) DOT 5 is silicon fluid and should not be mixed with the others. It's dyed purple so one can't confuse it with the others.
Ounce the system is properly bled and the master cylinder is adjusted, it should be fine. That's assuming that the seals on the master and slave cylinder are good.
One more thing. You should not be giving quick and short gear changes. You need to give the syncros. inside the gear box to do the job. Forcing a transmission to do quick shifts may bend the selector forks and wear out the transmission prematurely. It's not a sports car.