I was told that the Ben Ish Chai says to there is an inyan to light candles on zayin adar. Where does he say this and what is his source?
It is found in his Tikkun Zayin Adar. I couldn't find the sefer published online, but I did find a website which quotes at least part of it, in the middle of which it says:
וגם ידליקו נרות לכבוד משה רבינו עליו השלום, וכל המוסיף מוסיפין לו אורה ושמחה
It's about half way down the page. To find it easily just copy the words above into your browser's search bar on that page.