I don't do very well with fibre either, though there are times when I am more normal, when I can eat fibre. My IBS-D is up and down and I can go through days or weeks quite normal, or relatively so.
I was also looking for 100% soluble fibre foods some months ago, and got so confused I gave up. You're right; many foods with soluble fibre also contain insoluble.
I have tried fibre to help my IBS-D, and I can tell you it didn't work at all, just as I imagined it wouldn't! I don't honestly know why fibre is recommended. At my worst, I find going really low fibre can bring my gut balance back over the course of a few days, and help me to feel a lot better and healthier!
Then maybe I'll slowly reintroduce fibre foods I normally like, such as vegetables. Then I get to the point where I can even eat small amounts of brown rice and healthy veggies! Until the cycle starts again...and back I go to the low fibre foods.