Newbie z10 user stupid questions lol

Just playing around with my z10 that I won!! :D This is gonna be my thread for potentially stupid questions as I get to grips with it haha.

I have visual problems and wear hearing aids, so most questions probably to do with accessibility. I've upped the font to 12 which is great :D but I've noticed this doesn't apply to apps and stuff :/ Have been playing about with the magnify thing on my facebook on it. Is there any way I can up the font on the apps at all? Like on the 9900 it was set at whatever size right across the board. Quite disappointed with this as its like an iphone, which i couldn't use because of this.

Also is it the same for text messages as well?

Another app question, when in facebook and go to log out, it says if I log out, I'll lose all info and have to log in all over again, so I just shut it down then clicked the x in the box. Does this mean that facebook is always open? and running in the background? Its just I have a limited data allowance on my plan of 1gb so don't really want things running in background.

Also does the wifi need to be on all the time? Just using the home wifi at the moment.