I can’t advise whether or not intermittent fasting will result in weightloss in your circumstance, but I did want to say that Abilify is known for being rather weight neutral, are you sure it is a result of the medication? Could there be other lifestyle factors such as stress, overeating, or lack of exercise that could be contributing? Also, are there other medications that could be worsening your symptoms? I am only encouraging you to evaluate because when compared to a bunch of other mood stabilizers, Abilify is pretty weight neutral, so trying a different one may actually worsen the the problem.
Also half a pound a week is great!! IF generally takes a few weeks/months to start showing results on the scale, and because IF preserves muscle, the scale might not move much but your clothes will fit differently. Basically, give IF more time to do its thing and put the scale away from a month, if you are also watching caloric intake then you are sure to see results. Best of luck!