Hello and welcome to Android Forums crabapplez.
I'd be happy to answer as much questions as I can.

You don't really need an antivirus for android as I have had one before and it hasn't slowed the phone down as much as I can tell, but I think the battery fairs better without one and if you read app reviews, read the permissions, or ask the community about it you should be fine.
If you can you could get an expanded SD card for additional storage, but I think it's the phones internal memory that's important. Apps generally aren't too big as some are around 2MB or 3 depending on the app.
A screen protector would be a good idea as they're good to prevent scratches and all and if you keep your phone in your pocket along with keys than yes.
Sadly, I am not familiar with Talk Mobile, but I'm sure somebody here is.

The apps that come installed are usually things like facebook, youtube, Gmail, etc.
Some things like carrier apps too, but unfortunately you can't get rid of pre-installed apps unless you root/hack your phone.

For good battery life just keep the brightness down, don't use live wallpapers, turn WIFI, 3G/4G off, turn GPS off, and don't use task killers.
