Sorry to hear you are having so many problems with your new unit. Wow hard to believe that the installing contractor is MiA. Is there a governing body that this original contractor falls under? if so you should contact them as all responsibility is the original contractor,s. It sounds like you have tried to resolve this by dealing with the home warranty. I would not give up on the home warranty people as it sounds like you have a number of problems with your unit that requires a good tech. Since the techs they sent you were not able to solve the problem you need to keep the pressure on the warranty people to get them to send a good tech.