you need to define the parameters of a "survival kit."--you're asking the right questions, but one person's survival kit is a year's worth of storage, the next person's is a 72 hour kit. remember, some folks don't have more than a few days worth of food in their house. some folks have 6 months and that's not because they're prepping.
what i've done with meds is just try to short refill--24-25 days on a 30 day scrip and you can build up a supply pretty quick.