What's the ideal balance (forward/backward) in the saddle on an endurance road bike?
Should I feel completely balanced in the saddle, or is a little forward pressure normal?

There should be some weight on your hands when riding.  Not too much of course, but your setup is already slid back as far as it can reasonably be (saddle aft, 80mm stem), and chasing some abstract notion of fit when you're already at the extreme end of adjustments doesn't make much sense.
What's completely missing from your post: what happens when you actually ride the bike?  Is there any specific problem?  If not, just ride.  And maybe think about neutralizing your adjustments a bit as an experiment--if you put the saddle 1cm forward of max-aft, does the bike become uncomfortable?