aroundincircles

so I have a brand new 100 amp alt on my XJ, replaced just a couple of weeks ago. I've thought about adding additional lights to my XJ, but was wondering how much draw I can put on the system. when I have my jeep running with no accessories running it runs at what looks like 13 watts, then if I turn on AC it drops just below 12, and if I turn on the head lights, it drops another tick, and then when I turn on a set of fog lights I installed, it drops just a minuscule amount more.

1) is this normal behavior?
2) if it is, how low do I let it run... makes me a bit worried as i thought it shouldn't go below 12 to keep the battery charged.
3) is there a better alt to put on? the most powerful I could find was 100 amps.

Thanks. if I get a chance I'll record exactly what it is doing when I turn stuff on and off, but that always takes forever to load onto the net for me.