The extended file that you need is included in the zip, so you don't need to download anything else.
The version that you have now is too old and doesn't support Photoshop 2019.
A:
It is not possible. If you look at the output window, Photoshop will tell you something like this: 
"The file Painter.app/Contents/Applications/Adobe Photoshop CC 2018/Adobe-AdobeAudition.app/Contents/MacOS/Adobe-AdobeAudition" could not be opened because the digital signature was not valid
And: 
Could not locate file for key com.adobe.pkcs11.Registry at /System/Library/Security/credentials/com.adobe.pkcs11.Registry
This file is a cache of all the certificates used to sign Photoshop with and Adobe Audition. If you do not have one of these files, you can't install Photoshop. 
I would recommend updating to the latest version of Photoshop and Audition. 
I did find the 'painter' executable in the 'Contents/MacOS/Adobe Audition' directory, but no 'Contents/MacOS/Adobe.app' directory.
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Related links:

Adobe Audition CC 2018 V11.0.0 Incl Patches [Xforce Painter] Crack PORTABLE 📎