What is sold in the US as apple cider is basically just cold pressed apple juice with the solids left in. That means you have pectin in solution. Pectin is a water soluable carbohydrate that can trap particles in suspension. If you want to be sure it will clear, then add some pectin enzyme. That will break the pectin in sugar, and you shouldn't have much trouble getting the solids to drop out of suspension.
Ericbw, you probably had some pectin enzyme in the juice you cut the cider with. Most commercial apple juice is treated with pectin enzyme before being bottled. Either that, or you took the concentration of pectin down enough that it fell apart and released it's solids.
Hops do not alter how dry or sweet your brew will come out. I suppose you could mash some malt high, though that seems unnecessary.
I do cider on a regular basis, and this is exactly what I do. You can back sweeten with anything you like, but IMO frozen apple juice concentrate gives you the best flavor.
You can also fill a plastic bottle of about the same volume as the glass bottles you are capping, then pasteurize when the plastic bottle is hard to the touch. That gives you a guide for how much pressure is likely to be in the glass bottles.
This way you can bottle some dry, some semi-sweet, and some sweet. All from the same batch. I admit I frequently do batches of cider a lot larger then 1 gallon.
