Mike would normally respond to this sort of question, but he is out the country at the moment. I will answer as best as I can, someone may come back and post a better answer soon.
1) Normally once the car is equalised, it wont mater how many times you do it. So as long as it is done once that should be fine.
2)When you start an equalisation you will hear a loud beep to confirm it. It also takes a lot longer to equalise than just charging the car.
3)Battery number 5 does sound low, but I do not know at what point they should need changing.
4)There are companies out there who can change the batteries, if you do a search on ebay there are a few advertising. If you know someone who could do the work for you there are full instructions on the forums. It may be worth giving one a call and see what they say.
I hope this helps.