All the work you did to install the pressure gauge is only useful if the readings you got actually worry you. If they don't worry you, you wasted your time. And no, I have never wondered what my exhaust pressure was. I always assumed that if there was a hole in the exhaust system from the exhaust valve all the way to the rear bumper, the exhaust gas would find its way. 

Did that on my 78 El Camino 383 stroker one time, but there was a reason.  That is how you test to see if a catalytic converter is clogged up.  Test between manifold and converter.

It wasn't plugged, and was a total waste of time in my case also.  That was 20 years ago and have never seen the need to do it again.

I wish you lived close by because I have a million things that you could help me do that actually accomplish something!

What you have there is a data point. What you do with it can make it very valuable or worth nothing. Me thinks that if you make any mods and check that again, you will have another data point. Now the thing with data points is what do they correlate with? If you see a Horsepower improvement with a change in that point, you may have a lead to know what to try next for more improvement ( of course the opposite works too if you get a decrease, you may want to go the other way). I applaud the effort!