Yesterday I reseated the pump valves, reassembled the pump, then tested it on steam.
Most of the following video has the boiler at only 25psi, but I did run it off camera at up to 75psi.
After making the video I redirected the exhaust steam from the pump into the firebox. It actually seemed to improve the gas flame, maybe by acting as a blower. Not so sure about this being permanent though, because the exhaust steam contains oil from the displacement oiler, and I dont want that oil to be deposited in the firetubes.
I will make a water tank to supply boiler water. Maybe the exhaust steam could be passed through a heat exchanger in the tank, so the boiler feed water is preheated.
(if the video is not showing, click on the https link below)