Don't know where the working dir is on Mac. Why would you need it?
As to GEDCOM, many badly formed gedcom exists, you should after import read the message (if things went ok). You see in the bottom left corner of import also an icon if there were log messages. Click it. You can easily redo the import in an empty GEDCOM to test this. Problems on import can lead to errors using the resulting family tree. Tools-> Family tree utils-> rebuild secondary indices / rebuild reference maps/ remove empty objects, can all find problems and fix, post them to you.
Eg, If after an import the remove empty objects says it removed 200 empty objects, something went wrong on import ...
If you run a report and obtain an error, you should redo it, and post the actual message on the bug tracker.
There isn't a working directory per se. The configuration files go in ~/Library/Application Support/gramps, as
does the grampsdb database directory by default. You can change the latter in preferences, on the Family Trees tab.