How far can I raise my test scores, from going on a low FODMAP diet for IBS (Irritable Bowel Syndrome)?

I start fine then my IBS flares up and I skip a lot of the test and barely pass it. How can I improve my test scores from treating my IBS, or other things?

Since I was diagnosed with IBS, and taking the low FODMAP diet, I was able to raise my Athabasca University English free test from 53% to 63%. How far can I take treatment for IBS to raise my marks?

Link to free test