Gas mileage is gonna look like its poor if youre driving 8 minutes one way to work, the engine oil temps barely get to normal, if at all (depending on your climate and current temperature). Driving in ECO is ok in city traffic. There is a small difference in gas mileage compared to Comfort but Comfort keeps the car a bit more agile.
But occassionally do take your Stinger out for a run, these types of engines / cars almost 'require' some pushing every once in a while to keep them healthy.
Cabin noise; be wary with that, if it is just general wind noise etc, that is OK even though compared to what I've driven in the past, Stinger is very good in that department. If it is a rattle or a creak, then have a look around on the forum, there are plenty of topics about sunroof rattles or door creaks, those things can be fixed with some DIY (your husband surely can help if things prove to be a bit difficult) or have your dealership deal with it.