Monster power is not mandatory for receiving a key or organ but it is very much recommended.
1.) can keys actually drop without monster power enabled, as was suggested in the infernal machine blog? Or was this a mistake in the blog, and the keys will only drop in Monster Power 1 or higher, as was previously
suggested?Monster Power isn't required. At MP0, the drop rate for both the keys and organ pieces is 5%. At MP1, that chance increases to 10%, at MP2 it's 20%, and so on until MP10 (which grants a 100% drop chance for those items).
A full five stacks of Nephalem Valor is required, though, so just keep that in mind.
2.) since the chance for a bonus item to drop on MP10 is 100%, shouldn't that mean that any enemy that drops an item will drop 2? if the bonus item chance is 100%, no normal enemy should be able to drop only 1 item, right?
If you kill a monster while playing on MP10, and that monster makes its initial roll check to drop an item, it should have a 100% chance to drop a bonus item. So, yes, in that sense, the monster should drop at least two items. BUT, since the initial item a monster drops might just be a pile of gold, it's possible (with auto-pickup) that you may have just missed it. If you feel that something isn't working correctly, though, then please be sure to post in the Bug Report forum so our Quality Assurance team can investigate.
(Also, I saw this asked earlier, but the bonus item will always be a piece of gear, not a potion or gold or anything else.)
Magic Find does not have any impact on the drop rate for keys or organs.