My son has crohns and psoriasis, for him the psoriasis was an indicator of how severe his crohns was. After about 3 weeks his psoriasis had disappeared except for maybe a 1/4 of the size of a dime on his neck wear his collars rub. I would guess around 20-25% of his body was covered before starting ldn. He had large areas covering both shins, knees, elbows, chest, back, neck and top of his head, the head one was probably half the size of a cd/DVD and it looked like he was balding and he was only 11.
Within a week he also had more energy and was in a good mood instead of being tired and cranky all the time. His colds and common illnesses are shortened and he has greater pain tolerance, he rarely gets headaches so I can't answer that but it seemed to help maybe 50% with crohns symptoms, it never fully cured it on its own, we used diet and xifaxan to bring it fully under control.
It's been six years since he started and I just remembered and didn't include in my previous reply that after working up to 3.5 the doctor upped the dose to 4.5 and after a few weeks his psoriasis started coming back. It took a lot of arguing to get it back down to a 3.5 dose, some doctors believe everyone should be at 4.5, you should always experiment, if a higher dose results in better results, go with it but everyone is different and may have a better response with less.