In all my years using the dry pipe i only used 2 of the 3 orings. One that sits in the bottom of the pipe to prevent the pipe from clashing with the manifold, and one that sits on the end of the pipe, like the one in your picture.
Then i would use high temperature rated silicone and load the pipe cavity up with it. press the pipe onto the manifold, clamp down the kawi 650 style coupler, and let it sit overnight before using it. Worked every time and never had any leaks. the only downside was the extra few minutes of cleanup after removing the pipe again (to scrape old silicone out of the pipe).