You are approaching the problem from the wrong end. The second question has no solution, so it is easier to discern that first and subsequently not worry about the first.

Custom widgets cannot be read in foreign applications, and even standard widgets are not completely readable, because sending the GetText message to a widget may return a pointer to the string - alas the memory pointed to is not readable by the foreign process.

Your approach could be to inject a DLL into the C++ program so you get access to the widget values, or it could be to embed Perl into the C++ program, so you can serve the values out via TCP/IP, file, or whatever.

The solution to the first question is easy - TrollTech sells the Win32 version of QT.