Some basic questions

I appologize if these questions seem stupid or have been asked a million times before. I have my first batch of cider fermenting in a primary (6 gallon bucket). From what I was told, in about 4 weeks or so, I should be racking the cider into a glass carboy to allow it to settle out and clarify and then moving it to bottles. I was told to look for bubbles about 1 per minute before moving it over. However, most people on these forums say you should trust the hydrometer instead of the airlock. Is it ok to keep opening the lid on the bucket and checking the SG? I'm suppose to be keeping air out of the cider right? Also, what should the SG be before moving into the secondary? I started around 1.071.

I'm planning to move the cider into 4-5 1 gallon jugs after it sits in the secondary for a while. I'd like to add sugar to at least one bottle to carbonate. How do I know how much sugar to add? I assume too much can cause explosions and too little won't give me sparking cider.

Thanks for any help. I've only brewed in Mr. Beer kits prior to this and I'm going on the advice of an ex-coworker who had done a lot of brewing.

Trust the hydrometer Luke.
Yes, sanitize whatever will touch the cider to take out enough to fill your test tube and take a hydrometer after around 2 weeks. If your around 1.000 you can rack to the secondary to clear, condition, and watch.
I have not done one gallon carbonations, so I don't know the math, but I would caution to make certain the gallon jugs can deal with the pressure from carbonation. Most I have are not built for it.
I could suggest champagne bottles that you could cap, or reuse 2 litre plastic soda bottles. Just clean them up very well to get rid of any smells. They work really well with pressure and I'm using them more and more.

The SG for moving the cider to the secondary depends on how dry you want it to get. 1.000 is fairly dry - more like a white wine. Trust your taste as well as the hydrometer. What type of yeast are you using?

I use kegs instead of bottles for carbonation, but if you search the forum for "priming sugar" you can find info on how much to use for bottle combination.

I'm using Coopers. My friend said he used champagne yeast for a dry cider and ale yeast for slightly sweeter. I started talking to the people at my local brew shop and they said the Coopers was popular. I took their word for it.

I guess I was just concerned with opening the lid to the primary to take samples for SG. It seems like people go through a lot of care to make sure the airlock is in place and sterile to keep air out of the cider, so opening the lid to take samples might spoil it. Maybe I'm just over thinking it.

During the primary fermentation, the cider will be producing a lot of C02 which will protect from oxidation. I use better bottles for primaries and fill them fairly high, so that when I open them to check SG, the headspace fills up with C02 quickly. Also its easier to see the ferment. You dont really need to start checking until the ferment slows down. If you are using a bucket, that's a little harder to tell, but you can still go by airlock activity.

The main risk of oxidation and air exposure is that you can introduce vinegar bugs, although those arent likely to manifest themselves for months. If this is your first batch and it comes out well, chances are that it wont last that long anyway