Tincture of opium or hydrocodone slows things down, has your doctor tried giving you those? Have you done a defecation test?
Did you have a temp ileo? If you did, did the same thing happen with your pills coming straight through etc?
I see your take down was around 6 months ago. In the beginning my surgeon had me taking imodium and metamucil at the same time. I used the clear caplets filled with metamucil so I didn't have to mix with fluid and therefore took in less water than the directions said. We are to take in less water when we take them so they soak up the fluid. We still need to drink plenty of water but not when we take the fiber. I took imodium and mutamucil 3 times a day with meals and imodium before bed. I was told to take what it took. You can take up to 8 Imodium a day so start out with 2 each 4 times a day and take 3-5 caplets of metamucil 3 times a day. I went from that and cut down as my pouch got older. Imodium is like a super mild narcotic, or so I've been told. Therefore Tincture of opium is used by some with problems, which makes sense. I have chronic pain and take a pain medication with hydrocodone and know that slows my system down so I rarely take anything. When I do I take Imodium when I'm going somewhere for a long time.
The best food for stopping me up is a Bagel.
I don't mind a softer BM as it is easier to pass but it needs to be digested food and medication and supplements need to dissolve. I hope something above is new and will help. It's a hopeless feeling when your doctor doesn't know what to do next. My GI had the same problem and referred me to a different GI that specializes in IBD only. I would hope your doctor would do research, call another doctor or refer you to a specialist as mine did. If he can't help you please ask me for a referral. Mine referred me to a doctor at Mayo, it is only 4 hours away. There are other good places and doctors to go to that specialize in IBD and related problems. J-pouches are not real common so you might need to travel a bit to find someone that can help.
Please let us know how you are doing.