sometimes people in england get a better deal and can do both, but for most of us, you have to give up a room discount to get "free" dining. (which means that free dining is not really free after all, but it might be a good deal if you normally eat that way anyway.)
Nope. And that's why you really have to do your homework!! You have to be sure that the free dining promotions are really going to save you money!! I prefer to book my rooms at a room only discount and use my TiW card for food...but, that isn't an option for everyone.
Unfortunately no, you have to choose. Typically FD works out as a better deal at a value/mod (the RO discounts are usually a smaller percentage off of an already lower room rate). If you are staying Deluxe, however, you will want to run the numbers to see which saves you the most money.