The higher level character only gets 3x quest xp IF the quest is not grey to them. Also, you must be within 5 levels of the RAF's account to get 3x kill xp.

I would actually say that 13 levels is nothing worth sweating over, I personally would delete/remake the toon with a RAF account starting together, you can get to level 20 in an evening and level 30 with just a few more hours. but not using keyclone seriously slows down the process since only 1 toon will be doing the killing and ALT+Tab is slow (and i mean like Tandy kinda slow) to level and turn in quests. At the very least get TwoBoxToolkit addon, I get it from curse, but I am sure it's available elsewhere.