You could try ‘Enable chroma filtering for 4:4:4 sources when exporting via QuickTime or FCP. Even though your source might not be 4:4:4, I found it can be a solution for a (too) dark export.
As for the monitoring, when one of the exports looks different in comparison to all the others, it doesn’t what kind of monitor you’re using. You detect a change relative to others.
A broadcast monitor is always better though.