1. They're your rules, so I assume they would apply. RONR does not have such a rule.
2. Mail in ballots are only permitted if your bylaws provide for them. RONR has suggested methods, which do not include witnesses, but do include more than one teller, and the tellers presumably all observe one another.
3. If a meeting does not have adequate notice, then RONR's procedure is that it cannot be held. If it is, then any business conducted is null and void.