1987 Chevy S-10 Timing way off and valves have issues!

My nephew has been driving my s-10 to and from work (a "quick oil change" company), and in his care the timing gear seal blew. Instead of waiting for assistance and the right tools, he tore into it and did half the work himself. Well, we're pretty sure that the timing got messed up, only we're not sure how far off. Can lay hands on a timing light, however I'm afraid to even run the engine at this point.
After the seal repair, for some reason there is terrible clatter coming from the lifters. Sounds like the rocker arms are trying to beat their way out of the hood! Never heard any noise like this from this motor before. After checking the oil, he assumed that the rocker arms were loose, and tightened them down to some torque that required a six foot, muscle- bound man to break loose. (We pulled off the valve cover, and checked to see if there was oil coming through, and it was observed that only 5 of the 8 rockers were even moving, and there isn't oil coming out of all the correct ports.)

Please tell me what we've done to this poor little trooper of an engine, and what we do first in order to get her back on her "feet!"
I don't know whether there's a problem with the valves, rockers, or head now; possibly even the crankshaft? And the timing, how do we tell exactly how far we're off without dismantling the engine again?