K.C.
Only 7 oz in 16hours (9pm-1pm) doesn't seem like very much to me for a 5 month old. If I were you I would try feeding the bottle a little earlier (like noon) and see if he takes it then, maybe he is getting past his hunger.
If that doesn't wokr, don't stress he will eat when he is hungry. The more you stress, dread it, get frustrated, etc, the more he will feel that and feed off of your stress. Just try to relax. :)