We have a custom made font which we use on an iOS app. This font is displaced vertically respect the other fonts.
We usually used the ftxdumperfuser, but with the new El Capitan OSX release this app became incompatible.
So, is there any way to install this tool on El Capitan or is there any other tool to edit the ascender and descender of the font?
The most obvious solution would be to tell the people who made the font for you to fix the baseline alignment.
But, if that isn't an option, the simplest way to achieve this is to add a (or modify the) BASE table in your font, using whatever font editing tools you have available to you, for the scripts used in your font (if it's not specifically designed for non-western languages, that's typically just latn)
Tools like TTX or FontForge are free, powerful, and require a bit of learning how to use them, tools like Fontlab (currently on v5, we're all waiting for v6 to go on sale) are easier to use, but also "expensive".