Lori,
I've dealt with all that except the ibd. I don't know if laxatone is the same, but lactulose (need script in the US) is safe for diabetics. it's not digested or absorbed, it sort of coats the intestines to help move things along. Miralax is also good , start at 1/8 tsp twice a day, mix with bit of water and add to food. Will take 24-36 hrs to start working. Might ask vet about cisapride, it helps motility when they go. It comes in a chewable treat from Wedgewood pharmacy. Vet must specify chewable. Metamucil will add fiber, just check the ingredients, there are many varieties of the brand. You want pysllium husk as only ingredient, some stores sell pysillium powder. It took many trials with my girl to get the right combo and doses that worked. Eventually, the cisapride twice a day, miralax every night and the husk 3-4 times a week, subq fluids 2-3 times a week, it kept Ollie moving. Ollie never had an enema and the longest she went without pooping was 3 days.
Pancreatitis, pain meds, cerenia, ondansteron are needed and could be for quite some time. Your vet should keep you supplied with the meds at home, long term. I was introduced with Ollie's lasting 6 weeks. After that if she started a flare I could give meds immediately and could keep it from getting out of control.
I see there is a heart murmur. Have you seen a cardiologist? Ollie had one also, yet cardiologist gave a limit as to how much subq fluid she could have in a week. I purchased an IV line with a chamber that could measure accurately. It helps hydrate and vet gave me injectable cerenia I could give in the fluids so it didn't sting as much. The pills were to stressful for my girl. She also got b12 in the fluids.
Face Book has a Feline Constipation group you might check out. Good information there.
I will let others advise on insulin dosage, since there is history of dka, you don't want to skip doses or hold to long.