Are...are you fucking serious? You're really going to take this to court, over a stupid game, that will soon go on sale next month for %75 off and again at the same percentage during the Steam Summer Sale. The amount of fuck in this ticket is...just...damn.
You won't get far, as it's already been mentioned, your account could get termed. Is it worth that risk for an indie game? Also, I have not heard of any gaming company, Steam, Origin, GameFly, offering a %100 discount on any game, or a 'free' game, through the store page, these freebies are always sent through a provider and are accompanied by a key. The only time this is ignored is when the game in question is FROM the company, such as Valve, who gave away copies of Portal, twice. All you had to do was install it during the promotional period and it was yours.
If you are intent on going through and force Steam's hand, then Rest in Piss when you poof from the Steam Community, forever.
My two cents, but after having a brief chat, Steam is "Gonna break his fucking legs, for a 10 dollar game."