Accent LC (2000-05) :: Battery Leaking / Airbag Light On And Headlights Surging

I'm seeing the following symptoms in my 2001 Accent 1.6L:

1. Check Engine Light on;
2. Certain electrical functions occasionally surge. For example, headlights and dash lights will become noticeably brighter for a few seconds, and the heater fan will blow harder. The surges last for about 3 seconds, then stop. Surges happen randomly, sometimes four or five times during a 30 minute drive, sometimes not at all in an hour.
3. The speedo/tacho lights have been cutting in and out randomly for longer than this, and this does not happen at the same time as the surges above.
4. Recently, the surges became more frequent and the Air Bag light started going on, then off. Now it is permanently on.
5. The battery has leaked fluid out from the fill caps, a good few ounces of fluid.
6. There are no blown fuses.
7. The Battery is 6 months old.
8. The alternator is 6 months old, and is the third one after two previous ones failed; the original was replaced 3 years ago, and the replacement failed 2.5 years later.
9. A fried lead to the starting motor was found when the alternator was first replaced, and was repaired. Related?