Two of the screws on my neck pickup ring are loose, and last night I took out a loose spring and one of the screws. They're the screws in between the corners. A similar thing happened earlier in the summer, except that the pickup would sort of come out if I angled the guitar, but I got that fixed at a store. What should I do?
well its not good, get it checked out by a guitar tech, dont screw around with it by yourself
Will it cause any major problems?
Don't worry, they are supposed to be loose, you use those screws to adjust the pickup height for more/less output.
But are they supposed to come right out? And what about the spring?
Keep the spring in there. If they are still coming out, then something is wrong or you might have just loosened them too much,
One more thing: I lost one of my allen keys, the second biggest one and I can't open the nut or the bigger parts. Is there another way to open them without it?
not without risking breaking the screws off, there very fragile on locking nuts, just buy a 3mm allen key, there not that much