Hi there and welcome. Well, first I would say if greens, nuts, seeds, fruits, etc. are hurting you and making you ill then it doesn't do you much good to include them in your diet, right now. You would be doing yourself more harm than good.
I would stick with the foods that I can handle, and incorporate others a little bit at a time. I believe the VitaMix is pretty expensive, so I would make sure I would be able to use it before I buy it.
It is a good idea for you to make sure you get plenty of soluble fiber in your gut, before I would try too much insoluble fiber. I would still continue to grind, peel, puree, blend, cook well, whatever foods that give you a problem, and try small amounts at a time.
Look, I am all for fruits, nuts, veggies, seeds, beans, greens, etc, as I am a vegetarian, and I think they are extremely healthy. However, if they make you ill, you probably aren't absorbing the nutrients anyway, and you are making yourself miserable along with it.
I can handle green drinks and lots of insoluble fiber. If I don't get enough, then I don't feel as well. But, I wasn't always able to eat what I want. I did 3 rounds of the hypnosis cds sold on this site, and that was my magic bullet.
So, it really is a trial by error, unfortunately. You would have to experiment a bit, and see what you can and cannot handle. Slow and steady is the key. And it is more than the food. It's about relaxation, exercise, the stress in your life, daily temperature, travel, sleep, etc. So many variables play into IBS.
I hope this has helped. It took me quite a while to be symptom free, but it was well worth the effort.