What are dentist recommended fluoride toothpastes for adults?

Almost any. Really the most important thing is the mechanical motion of the tooth brush done properly and often. The tooth paste is abrasive and helps remove some of the debris but really the Fluoride is the most important component of the paste so as i tell my patients, the best toothpaste is the one with Fluoride that you use right. Don't buy too much into the whitening pastes either.
Yes. Most dentist recommend a toothpaste with Fluoride to maintain the prevention of decay, strengthening the enamel and help to some degree sensitivity.
ADA approved. I recommend any ada approved Fluoride toothpaste that tastes good to you and that you will use 2-3 times per day. Other than that, it really doesn't matter.