It's possible that the canibis oil might help some, but you're on 40mgs of prednisone (a very strong dose of a corticosteroid). I think you should use a stronger uc medication as well to get off of pred as quickly as possible, as you've already been on it a long while. Typically, you'd max out the mesalamine class of medications. You have the maximum oral of 4 lialda. The maximum rectal route medication is a 4g rowasa enema.
After mesalamine, immunomodulators (Imuran, 6mp, or aza) are often added. They're slow acting medications that take 6-8 weeks to work.
Some gastroenterologists go straight to biologics (entyvio, remicade, humira) as they're quicker working. I'm now on remicade and in remission (a lack of uc symptoms) for the first time since getting uc. It's true that they do have a statistically small and rare odds of side effects but few get them. A good read is this from the Crohn's and Colitis Foundation of America on the risks versus benefits of immunomodulators and biologics:
Moderator Ulcerative Colitis
John, 38, UC in histological remission
Rx: Remicade @5mgs/kg/8wksHell hath no fury like the explosion of noise and pinching from the 33gram fluff of parrotlet whom I accidentally woke on my shoulder