Ok. So im converting an old road bike to a singlespeed for easier transportation around the city (Philly to be exact). I have the bike stripped of all the parts and Im in the process of degreasing everything. I would like to make this as cheap as possible. So far it has been around $80 for everything (bike and tools). I have run into a few difficulties though.

-I am trying to remove the sprockets from the rear cassette and the wont budge. Is there any easy way I can get them off? Currently I am using the old chain to try and unscrew them.

-Im not sure how to remove the rivets connecting the two from sprockets. Can I just drill them out like any other rivet?

-Once I choose my gear combo I plan on using spacers to align the chain on the existing hub and bottom bracket. Will this work?

This is my first time really delving into a bike like this so please bare with me if you need any other information.