You are very much correct, you must use shims to get the LPR up to 100 psi before dialing it down with the newton adjuster (because of the way the newton adjuster interacts with the angel LPR it's necessary). That could be why your marker ain't firing and/or the leak. If there's any threaded parts on the LPR adjuster that don't have thread sealant on them, that could be your leak. And yeah, I'd always recommend using the parts the kit came with too (springs, and that). To check your reg pressure, you can use the LPR tester kit on the valve side of the marker (just screw it into the other tube, and I think you'll need a higher pressure gauge). Don't forget to regrease all the o-rings on your ram and LPR before putting them back in, and follow proper procedure for adjusting your ram stroke (should all be in the manual:
www.wdp.tv/manuals)