The male guppy should be okay on his own. And congrats on your fry! A 5.5g tank is okay for growing out a few fry but if you are planning on trying to keep most of the fry from your livebearers you might want to spend the extra few bucks and get a 10g. Instead of using water from your established tank, use some of your filter media or gravel - they contain most of the beneficial bacteria and should help you get cycled pretty quickly if not immediately. What to do with all your fry can pose a problem. You can ask your local fish store if they will take the fry - sometimes they will give you a credit, but they may not. Livebearer fry are pretty commonplace. You can also give them away on craigslist - don't be surprised if you can't actually sell them....