Maintaining a certain amount in one's bank account to avoid paying bank charges

Q:

1. If I have a FNB Islamic cheque account, and when I use swipe my cheque card I get E-Bucks, can I use this E-Bucks?

2. If not what can I do with it?

3. If FNB offers clients who maintains R50,000 as balance, then no bank charges will be charged, if the R50,000 balance is not maintained then a bank charge of R199 is charged, am I allowed to maintain the R50,000 and save on the bank charges? Or is this saving interest?

Giving fidyah on behalf of one's deceased mother

Q: My mother passed away a couple of months aga. She did not fast for many years because she was disabled from 20 years and also because of negligence. My question is, does fidyah have to be given for the missed fasts of the deceased, even though the years she did not fast is unknown.

My second question is what is the amount of fidyah to be paid for not keeping one fast.