It is true that rats are nutritionally better than mice but there are lots of just mice eaters out there. The difference are slight. The issue many run into is cost a bunch of extra large adult mice cost more than a large rat.

Typically I'd say feed about 10% of the snakes weigh a meal just change the times as they age. Your timing seems fine, unless you are in a hurry to breed a snake there isn't a rush you can feed every 5 or 7 days I usually let the snake tell me when it is time to drop back the timing. They often will start to 'hunt' in the nights and if they are doing that in 2 or 3 days keep up the 5 day cycle if it is every 5 days or so a 7 day cycle and if it is every 9 or 10 days a 14 day cycle.