As far as I am aware the primary option here will be to try to open the QVFs in Qlik Sense Desktop without loading the data (right click on the file and open without data).
If you're having issues exporting the Apps from the QMC then the binaries should be in C:\ProgramData\Qlik\Sense\Apps. Matching the names of the files in that directory (GUIDs) with the actual names of files can be done in the QMC by adding in the ID field on the filter (there's a toggle in the upper right hand side of the Apps screen in the QMC).
There is nothing we can do when the app gets corrupted. Probably we can recover the code of the app from the scripts folder and redesign the visualizations from that than to write the entire code again. When you open the app you see the URL of the app consisting of alphanumeric combination. Check for the same name in the C:\ProgramData\Qlik\Sense\Log\Script folder. Remove the timestamps in the file and run it again to have the code of the app. But the Visualizations have to be rebuilt again.
In my case the scripts were located at C:\ProgramData\Qlik\Sense\Log\Script, and the files had names like e1efc098-0ad5-4d7d-af2f-7d6b700c91f3.2015_10_20_13_12_28.807093E78F4B66863F4A.log. I had to find the one relating to the corrupted app, and then strip the scripts content from this file with a text editor.
I hope this helps you get your code back.