Your dosages sound a bit high. Why don't you try starting at 180mg DMAE for a week before going to 400mg. 500mg of B5 and 500-1000mg choline three times daily should be sufficient.
Some people claim to never notice an effect.
Others notice one in a matter of days to weeks. Everyone is different. If you're using soy lethithin granules, you may be allergic to the soy if you're getting a burning sensation. Messy but not too unpalatable.