Line types, colors, etc is always a topic for debate among fishermen, so use whatever you feel works best for you. If you catch fish and you're happy, then there's no sense in changing because of what someone else says.
But to answer your questions.
1. I use the same fluoro that's leftover from my other spools of fluoro that I use on my other reels, which many would consider to be a "premium" fluoro.
2. Yes. Abrasion resistance.
3. Then use whatever you think works best for you.
4. 18-36".