You are correct about heating flax seed oil and health benefits. It contains highly volatile unsaturated fatty acids that are broken down by heating and then unsuitable for action in their fatty acid form. Wondro is not a substitute for flax seed oil. Cold-pressed, unheated flax oil should be consumed separately for its health benefits, preferably emulsified with quark to improve its absorption as per the Budwig diet.
But with regards to sulfuration, the heat breaks up the elemental sulfur octatomic rings and chemically inserts the sulfur atoms into the double bonds of the fatty acids. These molecules are no longer essential fatty acids but rather acetaldehyde scavengers of a consistency similar to light crankcase oil.
Sulfur and molasses was used in a similar manner in days past but it was a mixture rather than a chemically reacted compound and was not as effective as the Wondro was, likely because the sulfur was still tightly bound to itself. The same limitation would apply to a mixture of flaxseed oil and MSM. The sulfur in MSM is embedded within the molecule rather than externally available for acetaldehyde binding. Your mixture idea would probably work better with something like lipoic acid where the sulfur is exposed.