Putting your tree outside with no acclimatization for a couple of weeks (outside in the day, in at night) or protection in e.g. a larger pot/box with mulch around it, was not a great idea, but taking it in again today once frozen solid, was not necessarily the answer either. I seriously urge you to get some books and start reading. You're trying to learn bonsai on an instant basis, and it doesn't work. Internet 'tips' won't give you any real basis for growing things properly or even styling them - you need a solid foundation on which to make good decisions and understand why they're made, both for your environment and for different trees. Repotting is done for various reasons, again something you should learn more about, not guess at, and once you understand it better, your trees will have a chance to thrive. Have a good look at
www.evergreengardenworks.com/articles (and the rest of the site) for a lot of basic, easy to understand information.