The B button should be a feature as it would allow players to extend their runs. Otherwise players would be finished the moment they fill the board really. Though I don't fully know the purpose of extending a run without a way to score it since really a player could just end turn without anything on the board and get the longest run. The only real indication for score right now is money I suppose.
You can probably indicate the turns income when the player hovers over the 'end' turn button in the text box maybe.