Hi Sandy,
Yes, those flare ups are horrible. It sounds like you are trying very hard to eat and drink as sensibly as possible, but IBS wins every time!
I can't eat oats either so you are not alone in that. I dislike porridge and always did, but love oatcakes. I bought the organic no additive kind, and used to love them with cheese in the 'old days' pre-ibs. (sadly, no more. I have to avoid cheese now.)
So I thought they were pretty bland food to nibble on but no. Every time I ate oatcakes I had to 'go' much worse the next morning. They ended up being a rather expensive treat for the wild birds in my garden.
I get what troubles you too, sometimes. Most days I do empty pretty well, but then go through phases of a lazy feeling in my gut, where I know for sure I haven't 'been' enough that morning. I don't know what causes it. When I go, I pass soft stool, so it's not constipation, it's more like muscles inside are lazy or something.
Bizarrely, when I have had more sleep that happens to me, and when I am slightly sleep deprived I 'go' much better! I don't expect that to make any sense to you, as it doesn't to me!
But when it can build up, then the body reacts and says "we have to move some of this back-up RIGHT NOW!!"
Thus a nasty flare up.
Sometimes I can feel a bit nauseous too in a flare. I don't think it's nausea literally from my stomach, but just from the disturbance, scary feelings, and exhaustion in my case. Or just the way the whole digestive tract gets shaken up by the dramas going on lower down.
I can feel so delicate in the gut after a flare, and my friends then are some gentle herb teas like lemon balm, meadowsweet, peppermint, camomile and blackberry leaf. Of course that usually means back to the super-bland white rice, eggs, and hardly any veg. diet for a few days until things settle.