1. Englehard in S.C.
2. Just be careful. I'd be surprised if Englehard will want to sell it in a quantity less than 25-50g, which will make 300-600ml.
3. It is a reddish brown powder with the consistency of corn starch
4. No. Use un-iodized salt.
5. Hot distilled water (120 deg F.) will help it dissolve readily. It usually takes 30-60 minutes for me to get it in solution.