How much should I be eating 3 months post-op from gastric bypass?

Whaever is comforrta. The purpose of a gastric bypass is to lose weight safely. The easy way to do that is to drink lots of fluid and eat several small meals a day. It is possible to out-eat your bypass and regain lost weight. Don't get caught in that trap.
Measure it. If you don't measure what you are eating, you will ultimately eat more. Try for four ounces of protein and 6 ounces of vegetables at a time. You can always eat more- but don't - part of a lifestyle change. Eat healthier- make it your mission to eat and find new vegetables, good fish, and learn to cook. Do not eat at the same places you ate before.