Point 3): If under the engergy saver pref pane you have selected "wake for network access," and you are connected to a router through Wifi you may also have the issue of your computer either not sleeping or waking up without warning. I actually had my notebook wakeup from sleep inside a slip bag when I went from my home router to a local coffee shop. The computer automatically was pinged by the coffee shop's wifi router and woke my computer up on its own. Thank goodness I pulled my laptop out of the sleeve shortly after arriving because the heat was starting to build.
Point 4): After you change your energy saver pref pane restart your computer and reset the the pram. OPTION + COMMAND + P + R during startup, keep all 4 held down and wait for the chime to ring twice and then remove your fingers from the keys and let your mac startup again. Verify that your energy saver pref are set where your want them to be and you should be good from that point forward.
The time machine issue has caught me a few times. Even if your are in the middle of a time machine backup if you close the screen or manually attempt to put your mac to sleep it won't sleep until that back up is completed. This goes for wifi and wired backups.
Hope this helps.
