I'm starting to realize how slow LF cameras are, especially considering the weak DOF at moderate apertures, plus the fact that there's not Delta 3200 available (wouldn't that be awesome?). Once upon a time, these things used to be used with flashguns and flashbulbs. How were they sync'd up? Did you have to run a separate PC cord from the flash gun up to a PC terminal on the leaf shutter (assuming it had one)?
Also, is there some trick to focusing on the ground glass? I was setting my infinity stops using a simple loupe, and even at f/4.5 it seemed like finding the point of critical focus required a lot of interpolation. I could see the fresnel clearly in the loupe and the ground glass image seemed pretty course and of course, small. If one was blowing up big prints, I can imagine the best possible focus could be important.
Earlier this year I finally fitted a fresnel screen to my main Crown Graphic, this improved screen brightness by 2½ stops and makes focusing very much easier, faster etc. (I do NOT recommend the supplier I used !!!). But as you've noticed Loupes & Fresnels don't really go together :D I find the fresnel means focus snaps in/out easily and accurately.
I use the camera hand-held most of the time (tripods aren't permitted at many places I photograph) and so using a loupe is not an option anyway. I don't have problems with focusing, and there's no problems with lack of sharpness with larger prints 20"x16"+, I use HP5 and normally stop down to at least f16, usually f22 @ 1/100th.
Many of the common Speed Graphic lens shutters are synced for flash. Unless it's a very modern lens it won't have a PC terminal though. Usually it's a bi-post. Others only sync via the solenoid which is actuated from the flash. The focal plane shutter, at least on the ones I'm familiar with, have a bi-post terminal as well, though the focal plane shutter needs a long duration flash bulb.
Some lenses may have an x-sync setting which could be used with electronic flash.
For focusing, are you using a dark-cloth? The focus hood on Graphics works, but a dark-cloth will help. Also you could try a loupe with less magnification.