The part you are describing is the gas block. It's not terribly complicated, but what you have experienced shows something is seriously wrong. I suspect someone has modified one or more of the parts.
My guess here is that someone altered the gas block threads. Ruger does use an odd thread size, which might tempt a guy to tap out the holes to use a more common screw thread. This might account for the block not holding together when firing. If this is the case, Ruger will not sell you a replacement gas block without sending your rifle to them. You can, however, purchase an aftermarket gas block from this website...
www.longmountain.com.
If the new block does not include new screws (I think it does), you need to get 4 replacement screws, the ones that hold the upper and lower halves of the block together. If you have trouble locating the right screws, send me a PM and I can locate some for you.
Aside from the above parts, there are only two others, the gas pipe and the gas port bushing. Although I normally suggest a reduced size bushing, in your case you need to put things back to factory specs before attempting any mods. Get yourself a new bushing and a new gas pipe. These are both very inexpensive through MidwayUSA.
With your new parts in hand (less than $50 invested total), you need to make sure the gas block assembly is reassembled properly. Be sure you get the right size Allen wrench to tighten up your 4 new gas block screws. You don't want a loose fit with the wrench on the heads of the screws. When you go to mount the gas block assembly back onto the barrel, check to make sure the orifice on the underside of the barrel is open and clear. As you go to mount the lower block half with the pipe and bushing in place, you willl need to "feel" the new bushing slip into the shallow bushing cavity on the underside of the barrel. Hold it firmly in place while you seat the upper half of the block into place.
As you proceed to tighten the 4 gas block screws, there are two schools of thought. Some believe a torque screwdriver should be used to set the screws tightened to a specific torque value. I'm not saying that is wrong, but I've never done it that way, mostly because these torque screwdrivers tend to have a +/- accuracy spread of several pounds. Instead, I just alternate from screw to screw and tighten them in a rotating sequence, watching the air gap on each side of the gas block halves to see that it is closing evenly. These screws should be good and tight when you're finished.
After you're mounted the gas block assembly, take a short piece of rubber automotive fuel line (about 6-8") and slip one end of it over the exposed end of the gas pipe on your mounted assembly. Gently blow some air through the line and you should detect the sound of air blowing into the rifle barrel. If you can't blow air through it at all, the bushing slipped out of the barrel cavity during the tightening process and the air flow is blocked. You will have to start over, and possibly replace the bushing again if it's damaged from tightening the block with the bushing out of place.