I think you can stop worrying. The $25 cover charges are only for the "specialty" restaurants (Chops which is their steakhouse and Portofinos which is a fine dinning experience). There are no charges for the main dinning rooms (which is by and far a very fine dinning experience) or for their buffet service area and many other food venues on the ship. So you don't HAVE to spend $25 to eat. Many people do eat at Chops just for the experience. If you are a steak lover, the $25 is well worth the price for at least one dinner during your cruise. But you do need to make a reservation the first day because the choice dinning times go quickly.
I have never tried to use cash to back up my sea pass account on RCCL. I have done it on Carnival. I will defer to one of the regulars on RCCL cruises for that answer. But I do not see why you wouldn't be allowed to do that. If not your option is to go to the customer service desk periodically and check you balance and make payments so that when you get off the ship you balance is $0. Just don't wait to the last night to try this as the lines at the customer service desk are very long on that night.
"Awful food" I think not. But every person's opinion is different I am sure. If someone if used to eating in 5 star restaurants everyday, then I can see maybe their opinion of the ships food can be negative. But a vast majority of people who cruise find Royal Caribbean's food to be excellent. Don't worry about it.
Carnival Cruise Lines:
Fantasy 90, Celebration 95, Victory 05, Conquest 05, Spirit 6/06, Freedom 6/08, Holiday 7/08, Victory 6/09, Valor 9/09, Dream 6/10, Splendor 8/10,Conquest 8/11,Magic 11/11,Triumph 4/12,Spirit 7/12,Freedom 11/12, Triumph 2/13 - The fire cruise
NCL Dream October 2006, RCCL Mariner OTS June 2007