Urgent: Online Gaming on PS4

Hey gamers,

So I recently got a job at a gaming shop and they put me in charge of the online gaming section.

So I need your people's knowledge if you would be so kind.

Here are my questions,

*item 1 How many consoles can I connect to a single PSN account for online gaming ? I have PS4s under which I want to sign up, and four ps3s. How would I go about this?

*item 2 How much data do games eat? I know some eat more than others and if you could give me a range that would be great.

*item 3 Besides the annual $50 for the PlayStation plus (which you need for online multiplayer right?) do individual companies like EA charge extra to play their games online e.g FIFa?

Thanks and your advice would be greatly appreciated!