On top of that the memory cards are so small, I'm worried that if I take my card out, I'll lose it.
They should release special cases for their memory cards that can hold at least five of them...for their dedicated customers.
Ok now I understand your problem. It seems that the only way to solve this, is to get a Vita below 1.8 (perhaps you know someone with a Vita who didn't update yet or you know a small retailer who let's you do this in his store with a used Vita?), switch to your account A on it, plug your memcard into it and then save your data on PC/MAC/PS3.
Sadly I don't know anyone. It's a Vita, noone bought the damn thing.