Installing oil pressure sender (idiot light sensor), Torque spec and a few other questions Options

[Chaznaster]

Just now, I replaced my oil pressure sensor as the old one was not working. Doing some homework, I found reference to torque to 15 lbft and nothing about crush or copper washers. There was no washer on the one I took out.

When installing, I hit 10 lbft (sneaking up on it) but after what to me seemed like quite a bit of additional tightening, did not hit 15. That got me worried that I might overtighten it so I paused and decided to consult with all of you.

My questions:
1) Is 15 lbft the right torque?
2) Does it need a crush or copper washer?
3) If I continue to tighten it, is it right to assume that the torque will suddenly jump up when the body of the sender hits the block?
4) If overtightened, what would be the worst case outcome? Stripping the threads? Cracking the case?

Thanks for your help with this one.