Welcome to the BBT charting train.
I'm not exactly the best person to answer this but I'll give it a shot:
1) It can happen, and 1 temp being exactly the same doesn't bring too much worry... But it could be your thermometer. I hear the walgreens one in particular gives similar temperatures over and over and must be avoided like the plague. XD So basically, it could happen, but it's usually unlikely.
2) I think it'd be best to take down the one where you woke up 30 minutes early as it prefers you to take your temp after at least 3 hours of sleep. 30 minutes won't make much of a difference in temp, I don't think. But if you stayed awake for 30 minutes while waiting to temp, it might give you a very different result.
3) It varies for person to person. I actually have fairly low pre-O bbts (96.5-97) in this board whereas some people have an average that's much higher. High temps isn't really a bad thing unless they make it hard to distinguish between pre and post temps.
I hope I explained some things to you. If ever I'm wrong about what I say, I'm sure the other girls here will clarify them better for you and correct me. Happy charting.