Shih tzus normally have between 4-6 pups.
Yes, you absolutely should stay with your dogs while they are breeding. Many times damage to both the sire and dam can occur.
And last, the pregancy will last from 58-63 days...approximately 9 weeks. :) Let me know if you need further information. :)
breeder/healthcare specialist
15+ years animal health care Hobby breeder of Olde English Mastiffs and owned by an English Bulldog