How long can I have the crown with open margin and open contact? (photo)

Sorry you are having difficulty with your new crown.  The open contact will eventually lead to decay under the crown but that usually takes a while to happen.  The more pressing immediate concern is the open contact.  If you are packing food between the teeth the gum will be very inflamed and infected and can eventually lead to decay on both teeth.  New crowns should not have open margins or open contacts and certainly not both.  A new crown can be placed on # 14 with very minimal effect upon the amount of tooth structure remaining.