The first and third ones, you should completely disassemble, clean out all of the old grease, regrease, and reassemble. They should work fine afterward, though they may smell oddly depending on what kind of grease is used. Not sure what kind of grease is used originally, might be some kind of white lithium... you could probably get away with general purpose grease, though.

The head spring isn't too difficult to adjust. With careful inspection, you should notice a small series of steps, upon which one end of the head spring sits. Try notching that end of the head spring up a step or two and see if that helps any.

The second one seems to have been mangled between now and then... If you find a Sony PC floppy drive, you may find a direct replacement spring. Otherwise, you can try to modify one from a different brand of drive. You're really not losing anything at this point, so no harm in trying, I guess.

The springs are relatively fragile, as they don't exert all that much force; just enough to put the head in full contact with the media. Too much force would pinch the media between the heads, which would ruin the heads, the media, or both, if the disk is even able to turn with the excessive pressure.