1: The reservation does have to be in the other person's name.
If the reservation is far enough in advance, MR will mail out a cert to the other person, who will need it at check-in. The mailing address of the other person is required.
If the reservation is too soon, they will express the cert to the hotel. The MR office sends a notice to the hotel by fax that the cert is on the way so that they will know this before the guest arrives. The mailing address of the other person is not required.
2: 1-801-468-4000 is the correct number, and it is only open M-F. You can get through to the "reward redemption" phone line Sat/Sun by calling reservations at 1-800-228-9290, and asking to be transferred. They can help you order certs, but not much else.
3: You are correct, it is farily easy to "take over" an MR account. You can contact the MR office and request that they put a four digit pin on your account. I still can't figure out why they offer the option without requiring it.