The crippled one seems like he wouldn't be very fun to play against... You need six seals to win, each one gives him a doom which means that he has effectively 13-6 = 7 doom track.
You don't need clues to seal gates, which removes a very very big part of the game (and the main reason to do anything but jump through gates full time), but nevertheless you NEED six gates to open in order for you to close them, which means he will be on 6 out of seven doom when the last gate to be sealed opens, barring any gate open encounters or funny mythos cards. Even one gate burst or double doom card would make him literally impossible.
So, you're playing, you seal gates very easily by taking madness. 5 gates have opened, you're doing perfectly, five are sealed, he is on ten doom. Sixth gate opens, doom goes to eleven, and someone has to rush in and close that gate right away before another gate opens, which will bring doom to twelve, and thus when you seal he hits 13 and awakens. So basically it comes down to hoping that you don't get a doom on those three turns. Lowering the doom track any further would make it I believe nearly impossible, but as it stands I don't think it sounds like a very fun game.
I would suggest getting rid of the doom on seals, and making the rewards offered by taking madnesses and injuries a lot weaker. As it stands doomwise he is incredibly difficult, but the rewards for injuries/madness are also incredibly powerful, so the only way to have a prayer is do nothing but abuse said injury madness rewards, which would make for a pretty one dimensional game.