Yes. Just use Play by Email instead - and instead of sending emails just post the turn summary manually (copy/paste) and attach a manually created savegame.
I dunno. I downloaded the save before you posted the error and worked fine for me. My guess would have to be either the download of the save game from the forum was funky and the file was incomplete.
game id is only used for tourney games, to identify the game.
you’d have to ask someone who has done it before, on the TripleAWarClub
I found out that the game-ID is used to distinguish between different games on the dice server.
So every mail that returns from the server has the game-id at the beginning of the “Subject”.