I can only speculate on what might happen since I do not know of anyone in quite your situation.
Many people get better then get worse and so on when starting LDN. I have a theory why, but I won't bother with that. Most do improve after several months of being on it, but it is not in a straight line. They suffer in between.
LDN is not a hard hitting drug. It does not even work like most drugs. The effect of LDN is indirect, so it works more slowly, and relies on the bodies immune system to clean up the problems in the intestinal tract.
All LDN does is trick the immune system into working harder, and hopefully, more normally. That is the theory anyway.
There really is no way to know how any individual will respond. It will not work at all for a minority of people that try it. Statistically, your odds are pretty good that it will work.
LDN is a treatment, and not a cure, so I would not expect perfection, and you still have to carry on your habits knowing you have Crohn's. If you start to abuse yourself, you will pay a price for it, but if you take care of yourself it keeps you pretty normal most of the time.
I have done exceptionally well on it, but I have other unofficial treatments I use also. I may not be as sick as others either. We all are different, but when LDN works, people are really glad they tried it. It changes their life.
I hope it works well for you.
Good Luck
Dan