Hey mate! While I'm a newb here, especially with software, Hardware is my niche
1. The port itself is directly soldered onto the motherboard, but to get at it you'll have to disassemble the console.
2. I'd use it sparingly and be sure to clean it off when you're done with a proper kleenex or something, I don't know specifically if that is or not, but if it's conductive it could kill your board on boot
3. It most certainly could have. I doubt it, and I have a feeling it's more the plastic in the port that's been damaged and rendered the bar useless.
4. Unfortunately I don't know. With the low voltage the Wii draws and the needs of LED's I'm most likely gonna guess it's only 3.0v.
5. Yep. If you find a ground and the voltage drop you'll get a reading (be sure not to short stuff out!) like I said of probably 3.0v
6. It's as simple as getting the sensor bar another 3/whatever volt source. (USB...!) All the port does is provide power, not data. You could even just buy a wireless sensor bar