I would suggest looking at the gas piping system. It may be undersized resulting in gas supply issues.
I too currently have ignition issues with a propane boiler. First, the piping was way undersized and the regulator couldn't keep up. Ignition was always a big problem, and it would sometimes lock out on ignition failure. Then, the supply piping was upsized (by the plumber) and a hi/low regulator system was installed (by the propane company). This helped a lot, but I still have intermittent ignition problems, and if any other propane appliance is running, I have bigtime ignition issues. I'm trying to get this fixed now, as the propane supplier says the supply piping is still too small.
My static and running gas pressures look good as well, but I definitely have gas supply issues, and I think you do too.