In reference to issue #3 It is in fact a bug that I am experiencing as well. A bed high in the sky, spectator mode, etc, you can't reuse the bed in that area due to the "mobs nearby" message when there are no mobs nearby (or even friendly). EDIT: Strike the above. I can't reliably reproduce. Below is still valid.

Also, the spiders weren't attacking me on spawn. They sat there looking really cute and glowy. I was in survival and they attacked after I hit each one but not before.

2ND EDIT: In peaceful I am still getting the "monsters nearby" message.

It looks like the way the mobs were being spawned caused some sort of weird resource leak on the chunk level. The world would say the entity is gone, but the chunk would say it was still there. Restarting the world or unloading the chunk would remove the outdated entity data though. I've changed the spawning code up so this situation doesn't happen. I also removed the ability for nightmares to happen in peaceful.