I'm sorry but I can't answer the first parts of your question, but here's an attempt at # 3.
I chose to earn points rather than miles, mainly because of the travel package options that Marriott offers. I can get a 7 night stay at a Catagory 1-5 property, and 120,000 airline miles for 270,000 points. I think that this is one of the best deals in the industry for "purchasing" airline miles.
If you chose to convert points to airline miles the conventional way, it costs 125,000 points for 50,000 miles. By using the travel package option, I feel that I enhance the purchasing power of the points-to-miles conversion process.