97 Blazer replaced cap and rotor with delco parts to try to cure a miss. Have found that the screws on rotor do not tighten completely. What do I do now?

 

The new rotor should have come with new screws and thread locker already on them. If the screws are stripped, replace them. If the distributor is stripped, you can try to repair the existing threads, tap new threads, or replace the distributor. The rotor is keyed on the under side so it can only be installed one way.

 

Its common for the plastic distributor to crack around the screw holes.
If you need to replace it:
GM CHEVY V-6 VORTEC DISTRIBUTOR ALUMINUM BODY

 

i would highly recommend the skip white distributor. no plastic parts on it.. everything is either steel (shaft) or aluminum (where the rotor and cap mount)

 

& half the cost to boot..............