I'm relatively new to fibro, and don't know the answer to your malic acid question, and I hope someone answers it, as I'd like to know, too.
As far as magnesium, I do know that not all magnesium supplements are created equal...I know the cheapest kind, magnesium oxide, is not very absorbable, but I'm not sure which one is the best...I take magnesium citrate, but I think there's another form that's even better, but I can't remember what it is...maybe someone can post that if they know.
Welcome to the forum! Lots of nice, helpful folks here. How long did it take you to get diagnosed?