Use selenium-objective-c framework
The reason you saw those issues is that the Selenium-Objective-C project used to for Mac only. In the Mac libraries NSPoint replaces CGPoint, CGSize -> NSSize
It wasn't all that much work to make it work for both, so I just checked in support for building for iOS.
https://github.com/appium/selenium-objective-c/commit/c27a5faf266719c87eda502718c90e350aba931e