Ad. 1. See my snippet. As I've said, it might be wrong, qmake can be nasty at times.
Ad. 2. OK then, that can be a problem. You can investigate usage of other build systems here: cmake, scons, qbs.
Ad. 3. AFAIK, target.path is a simple variable, it does not know about anything. That is why I proposed to create another one ("second.path") in my snippet above.