I'll try and answer your questions.
1. you definately need to apply some primer over the metal glaze and filler areas and sand it one more time. Paint can't be applied directly over fillers.
2. you can wetsand your clear and apply more, if it's a 3-1mix I would keep the ratio the same and air pressure.
3. you shouldn't need to wetsand your basecoat between coats, if you like you could just knock any nibs off between coats if you let the paint flash long enough but there shouldn't be any need to sand the whole car if the paint is going on alright.
4. I don't know what your carport is like to spray in so I really can't make any suggestions there but watch your health and make sure you wear a good mask with the door open and or fans to get the fumes out.
5. no experience with endust yet.