Well, in regards to Satan being forgiven...
As far as I know it for the Lutheran church (I am a LCMS Lutheran, for contextual purposes), it is believed that any and all sins can be forgiven,
except one. The only sin that cannot be forgiven is to thoughtfully choose to turn one's back against God, and to not love God out of personal choice. (I know there's a scriptural reference, but unfortunately my mind's blanking... it's in one of the Pauline epistles, I do believe... or maybe Hebrews lol...).
Satan turned his back against God. He had put his own selfish ambitions above God, in hopes of becoming as powerful as Him. So, as far as I can see it from the Lutheran perspective, Satan cannot be forgiven for what he has done.
I don't even want to go into theoretical ideas like "well what if Satan was sorry" and all that jazz, because as far as we see it, Satan's sticking to his guns until the very end.
If I can think of the verse(s) that went along with the viewpoint listed above, I'll try to remember to post it here later on just to put it into context... or, if you want to dig through
www.lcms.org/ctcr to figure out more thoughts that the LCMS has upon theological issues, that's cool too.