I know your post was quite some time ago, so unsure if you have had improvements with your issues. It takes time for your body to adjust, and you need to adjust how you eat, and maybe even what you eat. Everyone's a bit different.
I have had my J pouch for 17 years. I discovered metamucil caps a year ago, and it has beem a life saver. Less liquid poops and much less occurring butt burn. There isnt a lot of support out there, and people dont like to discuss this topic. Surgeons aren't much help in my experience, as recos are normally directed to medicine or surgery, and less focussed on how to use metamucil and food to naturally slow output.
For the past year, I take 1 to 2 metamucil capsules with every meal, plus anytime i drink alcohol, coffee etc. I base it on what im eating too, like if i eat oatmeal which is binding, i can get backed up if i have too much metamucil and that is really uncomfortable. If i have alcohol or mostly liquid or spicy food, i take a few more, as it helps to absorb the acid or spice - which helps reduce frequency and butt burn incidents.
Now i am trying to solve my nighttime incontinence. I decided to try the powder form of metamucil so i can increase my doseage, but capsules are too expensive to use just to increase fibre. I also try hard to not eat after 9pm, or i am guaranteed to have a nighttime accident. I may introduce immodium at night, but im trying to do it without meds first.
Let me know how you are doing. I hope the above info is helpful.