N.J.
I am so sorry to hear this, I know you are committed and want to continue nursing. I'll tell you what I would do. Nurse first and then offer a bottle. If he truly is not getting enough, he may take the bottle pretty easily or Daddy may have to offer the bottle to him. I'd start with 4 ounces. If he doesn't seem satisfied, then add formula one ounce at a time. I am of the opinion that until they are a year breast milk or formula is best. I wouldn't increase his food, it sounds like he is eating plenty of it already. Another idea is to mix formula in with his food. Skip the juice, he doesn't need it. To answer your question, according to Parenting Magazine he should be eating 2 jars of Stage 2 food a day and 7 ounce bottles for a total of between 28 and 32 ounces a day. At nine months I think the bottles should increase to 8 ounces. I can't find my magazine, with the chart, but here is a link to a good article.
http://www.parenting.com/gallery/Baby/The-Truth-About-Fee...
Best of Wishes!
N.