Black out dates:
Are you referring to the Power Pass black out dates or special rates at the onsite properties?
If you are referring to special rates, usually there are not many discounts during major holidays. July 4th and the few days before and after traditionally have had higher rates than later in the month or earlier in June.
As for booking and deposit, different reservations have different rules. I believe there are some Universal Vacations that mandate full payment 45 days in advance. Not sure what the refund policy is on those, as we never book packages. We have always found it to be cheaper to book everything separately.
If you book hotel room only through Loewshotels.com or the universal website, it tells you it will charge your credit card for one night's stay. This deposit is completely refundable up to 5 days before your scheduled arrival date. However, those on this board, myself included, have never been charged the one night's deposit when booking online. However, that does not mean that it absolutely won't happen.
They usually DO charge the one night's deposit if you book the hotel only by phone, either with Loew's reservations or through Universal. But again, this is one night + tax, and it is completely refundable up to 5 days before arrival.