first of all i wanna say that you are doing fine and you shouldn't have any problems with your cider
even with that small hole, there would be a blanket of co2 on top of the cider that will protect it from oxygen, so that shouldn't cause any problems.
Montrachet yeast does stink quite a lot when its fermenting. Search Apfelwein or Rhino Farts and you'll see thats really common. That smell will not be a part of the flavor once you remove the cider from the yeast.
I don't know how long exactly you have had your cider in your primary, but once the yeast start doing their thing, the cider will become extremely cloudy and will stay that way until the yeast begin to die and fall out of suspension. The cider will clear in time.
As to the length of time that you want to let it sit... If you plan on letting the cider go completely dry (especially with all that added sugar) the longer you can wait the better. It will be drinkable in a month, but it will continue to get better and probably hit its prime somewhere between 6-10 months of aginging.
I hope this helps