I'll give a go at your questions though just to try and be helpful. The organic's forum is packed full of great people and info, it can be a little rough around here though sometimes. We just get a lot of people around here asking the same questions.
1.) A soilless media is a growing MEDIUM that has NO soil in it. It is comprised of peat, sphagnum, barks, perlite, etc. It has almost no nutrient content to benefit your plants.
2.) People are using soilless because it lets you custom tailor your grow and such to your plants needs. You basically give them exactly what they need when they need it, not relying on your soil to provide any nutrition.
3.) Soilless media does not affect your medium in a bad way at all. It works perfectly with it. I use pro-mix orange with the added mycorhizzae and add more myco throughout the grow. As long as you nurture your microbes, they will thrive in any soilless medium the same as they would in soil, maybe more since you are able to add stuff that would benefit them and make them multiply, ie molassess, sugars, and more myco.
4.) Molasses is a by product of sugar cane or sugar beet processing which turn the cane or beet into sugar. The plants like it as it has some potassium in it, but the microbes in your soil love it even more. It is a carb that helps them multiply and super charges them helping break down the foods in your soil to make them available to the plants.
5.) not really sure
6.) explained in 4
7.) I personally think that molasses is really thick and should be used in lower doses. Maybe 2-3 tsp/gal rather than 2-3 TBS. A little goes a long way.
8.) I don't use molasses during flush, mostly I am just using either pH balanced water, or water with Thrive Alive and mycorhizzae to help chew up the remaining food and help speed flushing.
I am by no means an expert, nor the most intelligent person in the world. I am sure there are other people who know more than me who are looking at this right now. If I made any mistakes, be sure to correct me, as I love to learn something new.
I hope this helps and gets the ball rolling for you. Happy Friday, blow one for me, cause I'm blowing one for you, lol.