Try the detox methods cited to you (in the threads) and then slowly up the MSM bit by bit?
If the MSM is shifting stuff so much that your nerves are hurting and complaining, then I'd say you need to pay attention to those signals. <:)
The schools of thought I have seen related to pressing through herx reactions have been mostly in the midst of internal Iodine usage and parasite cleansing. In both those cases, it's a dieoff of infections and parasites that are generating the ailment.
By the way, it comes into my mind that rosemary is quite good for the nerves! An accquaintence of mine is interested in herbology and made up a tincture for a friend, reported excellent results.