CONGRATS on your new kiddo - she sounds adorable! I would get her plenty of chew toys and chew bones and perhaps a Kong - and redirect her any time she chews on anything else. You may have to limit her access to the house though until she gets through the teething.
Spaying is recommended, generally, before the first heat. I did Pfeiffer's at 8 mths old...a little later than most. Also, you'd want to have the vet remove any retained baby teeth when under for the spay -- and get her microchipped at that time too.
As far as feeding, 2-3x a day is perfect and that's a nice food you're using. As far as how much to feed - you may find this calculator helpful:
Dogs feeding chart - Nature's Logic