Is there a suggested range for how close the pickups should be to the strings? I probably messed it up a long time ago. Also, one of my single coils rattles around a bit. Is there supposed to be a spring behind it that pushes it towards the strings? any way for me to fix that?

Also, I find that if I'm picking over one of the pickups, i hit them quite a bit. So far it hasn't been a problem, i've always picked between the pickups (S/S/H). Is that something i should work to fix, or is it normal? H/S/H configurations cause some problems for me.
Manufacturer settings usually have pickups between 1/4-1/2" from the strings, give or take. Yes, there is supposed to be a spring between the bracket on the pickup and where it mounts to the body to make it stable. Any guitar shop should be able to hook you up with a replacement. Hitting the pickups with while picking is a technique issue. You should be striking the strings with only the very tip of the plectrum.
Hi, I'm Peter
Fender recommend the poles of their single coils should be 2.2mm away on the bass side and 1.8mm away on the treble side. That's from the handbook that came with my guitar.
The Laney Thread are big and clever. No exceptions.
it depends, if the pickup is closer to the strings it'll give you a sort of volume and fullness to the sound. if you lower the pickup away from the string, then the pickup is able to "hear" all the harmonics better and your tone gets a bit clearer. Lowering my pickups was essential for clarity while being tuned to A# standard. (6 steps down)
Grammar and spelling omitted as an exercise for the reader.