Blackjack player status

there's a variable or a way to set on trigger conditions when a player "stand" ?

Selection's Status in the game is Stood

also there's a way to reset back amount to default at midnight ?

Use the action "set default back amount to...." and in the conditions specify:

Current Time is between 00:00:01 and 00:00:10

This trigger must be active, i.e. constantly checking the current time.