OK Frank I got them as well, I cant see where you tied into the relief valve but the boiler drain tee you used sure does look like it's 3/4 inch to me, it appears to me that your main supply manifold is 1 inch and reduced to 3/4 on your last heat zone, you have some major flow issues in the near boiler plumbing and if you were my customer, I would suggest ripping it all out and rebuilding it on a wall with a minimum of
1 1/4 inch main loops, the main loop is where the injection from the heat exchanger should be, doing this would ensure proper flow, neaten up the near boiler plumbing and make the system much more serviceable. I'll try to post a picture of my last manifold job to show the difference.