The FR trem system is capable of handling any gauge of string you want to use. Most players who use them install 'spider web' gauge strings, but that doesn't mean that you have to.

You will need all 5 springs. Be prepared to spend a lot of time fiddling with the settings to get it right. Again, that's not because of the heavy strings - it's just that FR trems are a major PITA to get set up properly. Once the initial setup is right, it should be stable for a long time, so the first-time hassle does pay off.