With the current state of the graphics repo (which contains your previous changes for this bug RT-27891) and with the build from the sandbox I get the following problem. If I revert your changeset for the previous phase everything works fine.
When running an application which uses the JFXPanel on the Mac it hangs on the startup. The AppkitThread is waiting for the renderer to finish its job and the renderer is waiting to get the job. This deadlock could be easily reproduced with the HelloJFXPanel app which is in the repository in rt-closed/toys

I have attached the thread dump.