So I'm doing G.I. Blues, and realize at the end as the NCR are shooting at me that I never told The King about the beaten envoy. No problem, except all my saves are either from the last 5 minutes or 10 hours ago. So I try to reset the quest, and that was everything got messed up. Long story short, I'm now in a place where I've reset and started the quest over, but can't progress due to Roy (in the Old Mormon Fort) not talking to me. When I try to setstage to later in the quest, it just won't work, or the King won't talk to my about the quest. If I use completequest, the King won't work with me for Kings' Gambit.

What can I do to fix this mess?

Roll back to one of those earlier saves from before you neglected to mention the envoy to the King and before you hosed everything up with console commands. Unfortunately, using the console to manipulate quest outcomes and stages usually screws up more things than it fixes.

I would, but the only saves I have from before it are a ridiculously long time ago. I'd prefer to find a way to revive this current save.