Raedf. Welcome to the forum.
To answer your questions:
1) It doesn't specify whether you can use someone else's credit card to pay for your EOI so I guess you can give it a try.
2) 120 points without a job offer is normally OK but, if I were you, I would check thoroughly whether you are entitled to those 120 points with your work probably being outside the comparable labour market.
Have you read through the
Expression of Interest Guide ? There is a lot of useful information in there that may be of help to you.