Quality of time lapse from images
You are approaching the problem at hand very well, you have however not used the most quality-preserving solution available. 
I recommend that you take your raw image files and import them into Adobe After Effects as a camera raw sequence. This will let you work with the files directly in their raw format and therefore retaining the most quality. From there, you can choose to export in a lossless format if you so desire.
Using this method, you should see a better quality from ProRes 4444 than ProRes 422.


Best of luck