If it's a pre-'99 length bolt, it's too long with that post-2K backblock. With the bolt and pin in place, pull the block all the way back and see if you can see any of the bolt through the feed neck.
And yes, the O-rings might be swollen a bit, at least if they're black rubber. Throw on some fresh tank 'rings and try a faint dab of lube.
As for the operating pressure, it very much depends on the gun's setup. Depending on which valve and springs it has, it could need anywhere from 180 (if it has a Tornado) to 300 or even 400. You'll likely need to 'sweet spot' it- instructions can be found with a search on MCB.
Basically, you start with a low pressure, and shoot it over a chrono. Keep shooting as you slowly crank the pressure up, and eventually you'll find a spot where the velocity starts to go back down as you increase the pressure. Find the point where the velocity is the highest, then fine-tune with the IVG from there.
The eye screw is a 4-40 countersunk, 1/4" long.