I don't really have much help to give you since I killed my cogshall mango. I think it died from fertilizer burn. If they have Cogshalls at the Mango Festival @ Fairchild Gardens in Miami, I probably will buy another one. I tend to kill my plants with over care:).

Anyway, maybe your mango is root bound. Try putting it a bigger pot, about one size larger and water. That's my suggestion.

Good Luck!!

if you can post a pic that helps some times.
just some guesses from my experience. Often when plants are greenhouse grown or shade grown (fresh from the store) when you expose them to full sun the old leves get toasted. Hopefully new leaves will start to grow and these can handle full sun.

Splitting of the main trunk can be bad, scratch a small portion of the bark on the opposite side of the split. If it is green there is hope. If you scratch and the wood is dry try another spot, if nothing is green (or it looks yellow) you tree might be on it's way out. If this is the case dont throw it out, maybe it will grow suckers from the roots and you can eventually regraft it. Or some stores have 1yr guarentees on there plants, grab your receipt and take it back.

just my limited experience, good luck,
-Ethan