I understand what you mean. I think it's really easy to get something bordering on an eating-disorder with IBS, because of all the anxiety around food.
Doing elimination tests can be quite tricky. If you want to you could ask a dietitian for help and either do a basic diet and then add new stuff in one at a time or try to eliminate one thing at a time. I think the general protocol is, if you start with a very basic diet, to add in one new thing at a time every 2 days or so and then if you think you have a reaction to something, eliminate it again and then wait till you stabilize before adding more stuff in. Then you should do a second round with the stuff you think might be bothering you. This is so that you can see if it's really the food or if it might have been something else, like stress for example.
About the pelvic floor muscle problems: I got an autoimmune paralysis from waist to toes from a regular cold virus when I was 12. I recovered pretty well but my right leg is still partly paralyzed and my pelvic floor muscles don't work properly. I also have bladder emptying problems. The combination of IBS-D and not having normal sphincter function is stressful so I have been through tests at the surgery department and this fall I have been going there once a week and doing electrical stimulation of the sphincter and also biofeedback training, where I can see what happens when I try to use the muscle. Unfortunately this hasn't helped so now I am waiting to try a procedure where they put electrodes in the lower back. They then stimulate the nerve connecting to the sphincter. If that works they will put temporary electrodes in and connect them to a pacemaker. I hope it will work as that would probably help prevent any future problems related to a weakened pelvic floor.