If you haven't been letting your water stand overnight before you give your tree a drink, I'd recommend that. This'll give the mineral at least a bit of a chance to particulate out of solution. I'm guessing you have hard water. In heavy doses, the lime can raise the pH of the compost, though ficus are hardy suckers.

As for other trees, try another sort of ficus--I recommend both Green Island and Golden Gate, though there are seemingly innumerable cultivars of Ficus microcarpa to choose from. If you'd like to move to hardwoods, Chinese Elms will keep you busy, and among the conifers the junipers are tough (everyone likes the shimpakus, though I think the procumbens are great as well).