That's what the voltage regulator on the alternator is for. You ain't gonna hurt anything; the system is only going to take what it needs from the alternator.
Exactly. You just got to remember 3 things: (1) you need to make as many amps as you consume (at least!), especially while idling (otherwise, you will drain the battery), (2) that the closer you get to an alternator's capacity (meaning if you are pulling close to what the alternator is producing), the alternator becomes hotter and thus looses efficiency, and (3), the more current draw you put on the alternator, the more horsepower the engine will need to divert from the wheels to the alternator to drive it. If the alternator is under used, there is no problem, as the voltage will remain steady (should be at about 13.5~14V).
