Life and purpose have as much value as one applies to them; the reason is that from God's perspective, knowing every outcome and every possibility would mean that either everything happens for a reason or else nothing has meaning. If all of the events that have transpired are working to a greater goal, because of their influence on one person and those ripples eventually influencing mankind. If God isn't a fatalist because there is no set outcome to human events and all works towards no end, ergo nihilist.
Just like knowing that your son is going to kill someone does not equate to you putting the gun on his hand. The matter is not if God created Satan's faulty or not, God could had avoided the events but didn't. Probably because he took the Devil's bet that mankind aren't worthy, but the intent for such as thing would bring God to human level.
The son in question is not free, because his father has looked at the future and every action that the father will take is influenced by that view. The choices that the father takes afterwards could change the son's future. If the son future rest on the father's influence, where is his free will?
Compatibilism requires an amount of "self-reference" in order to work, the son must be aware of every choice he makes (even the unconscious ones) in order to truly have free will. Otherwise he is just following a set of predetermined events.