The MAX variable values do not pass across jobs. When a saved job is picked up the Hotfolder a new job (with a new jobID) is created. The FFCore variables are in the default state for a new job.
Unfortunately, the External node does not allow for the writing of new variable values with the exception of xpf (job ticketing). There is a variable $FFwfDoc.preflightResult$ that may be useful.
From what I understand the MAX Variables travel with the files as they are passed along withing the workflow they are directed to, but they would not be passed along to the finished PDF (Unless you used the PDF Job Metea Data Fields to store this information).
IE in your workflow you could Add an Optimize and then [Override PDF Document Properties] and then place the variable in 1 of the 4 PDF Properties: You could probably put more than 1 in the Keyword spot but it may be difficult to parse afterward.
There are more Metadata Fields but I am not sure you can change them.
As for question 2 I do not know if you can change any values other that the ones mentiond above in the PDF.
I prepared HotFolder with about forty MAX variables. In WorkflowDestinantions section I created routing roules to 9 Workflows where presets settings are based on this variables. Everything works fine :) but I have 2 questions:
1. Is it possible to copy/move MAX variable values with job to the next Workflow (e.g. ending the path with saving to the next HotFolder or by any RoutingRoules (like in main HT)?
2. Is it possible to change the value of the selected variable during the process, (e.g. when I receive preflight status I would like to change the MAX variable value from No to Yes)?