Yes. When you are over weight, the extra weight you carry around will add to your shortness of breath. Also, the pressure your belly fat pushes up on the diaphragm, will increase your shortness of breath. Losing weight and increasing your physical fitness will help you. In order to do this, you need to have your asthma symptoms under control first. Be sure to see an asthma and allergy specialist.
Probably. At the very least it will decrease reflux, a known asthma trigger, but it is likely to help in other ways too.