glad I asked about the cod liver oil. what about the benfotiamine?

You can still do the benfotiamine. It is for other aspects of nerve
functions. There are people who have genetic problems with thiamine. (Asians for example who flush and get ill drinking alcohol are examples). But anyone consuming sugar and alcohol could use benfotiamine as thiamine gets used up quickly with dietary habits. Some people find benfotiamine very helpful and others less so. But it is not harmful, for the most part.

Don't assume your magnesium is doing any good if it is OXIDE form. This is a common in many supplements still because it is so cheap. A chelated one is best. or SlowMag which was made for doctors to prescribe, but is over the counter still.
This is my magnesium thread:
http://neurotalk.psychcentral.com/thread1138.html