If I pay enough to buy the season pass on Itch, will I be able to play all the episodes on Steam? Or does the Steam key only include the first game? Just trying to figure out whether it's worth braving the US currency conversion or better to buy directly off of Steam.

Itch will only give you episode one Steam Key, since it's not set up to distribute multiple keys. If you decided to purchase on itch and would also like the pass key for Steam, send me an email, from the same address you made the purchase with:  portablemoose@gmail.com. 

Okay, thanks for letting me know!