I'm no technician, and you have already gone beyond what I could do, but in saying that, it also sounds like you have run aground yourself.
I think you may save yourself a lot of time and hassle by looking up a fairly local repair centre who can sort your issues out. Regs can need special skill to set up as well as tools, and since you have had the gun in bits several times now it could be something is wrong your just not seeing or the reg is just toast and will never work? So you could be totally wasting your time here? My main point is - you don't have a problem that someone can just say - replace x/y/z and it will be fine, it sounds like there are several problems combining to give you a general headache.
I know this is not the answer you were looking for - but it would solve your problem in an effective and less frustrating way.
James