When considering a new food, have one serving of it, and then don't add any new food at least that and the next day, to see, if you have any symptoms. The safe method is to try one new food every 4th day.
people can safely eat 25-50 g of fructose "at one sitting". Fructose malabsorption, officially is condition, when you can't safely eat 25g of fructose. Now, some with FM can safely ingest 20 g, but other can't have even 5g. Depends on severity of malabsorption.