I think most or all of the problems you described would be solved by renting a proper professional sprayer. All of the home improvement places and most paint stores rent them. You just stick the uptake nozzle into your five gallon (or smaller) bucket, obviating the need to change so often. Even if you do need to change, you just flip the switch to ‘prime’ and it gets all the air out. Mask the ever-loving Spaghetti Monster out of everything you don’t want painted. Practice with the gun and nozzle so you get the spray pattern you want, keep the right distance, and overlap without overdoing it. It’s quite a bit easier when you just have the spray gun in your hand and don’t have to lug the jar of paint around attached to it. It does take some practice, but you can get really good results if you let yourself.
No!!! Wear a proper respirator mask with appropriate cartridges that will keep atomized nastiness out of you breathing passages and lungs. Whoever you buy paint from can help you out with that.
