This one has been hashed out quite a bit.
Try this thread
http://www.homebrewtalk.com/f11/5-gallon-culligan-bottles-27398/?highlight=culligan to start, that should help you get an answer.
I wouldn't try and put a 5 gallon batch in a 5 gallon fermenter, that will be really messy. If you do a blow off tube is mandatory. As for scaling recipes, check out the brewing software forum, most of the major software have free trials and there is some excellent free software too. You can also post to the recipes forum and get assistance.