I would guess that I've got about twenty hours on an oil change on my Bravo 1X. Is it normal to have to add fluid to the resevoir? It's not belos the low mark but it's lower than I remember. I haven't seen any oil leaking out nore residue on the lower unit.

Yes always have to top off at least once after a change.Just don't fill too much if you don't have drive showers and you are going on a long run.Learned that the hard way.

After running a couple hours , any air will get out and the gear lube will drop maybe an inch in the bottle. If it is loosing after the first hour or two, there is a leak somewhere. If you don't see it leaking anywhere, then its probably leaking from the rear seal into the bellows.

I recently installed a Simrek Drive Shower. We just got done with a vacation where we ran pretty hard and towed about 2,000 miles. Everything is running smooth and no indications of a problem. I'll top it off and watch it closely. If I'm reading your advice correctly I shouldn't see another significant drop. If so there's a problem, correct?

Yes

Correct. My gear lube does not drop at all in the reservior except for maybe the first run after a gear lube change. I was loosing about an inch in the bottle every 10hrs a couple years ago. The rear seal on the drive was leaking lube into the bellows.