well as long as the engine and tranny are mechanically sound i dunno if i'd jump to selling it so quickly. all the things wrong with it, if you can resolve them, are fairly minor. just figure out where those wires go to and remove whats not necessary. he may have had like neons or led washer nozzles hooked up, who knows. try swapping back to a stock fuel pressure regulator if you can get one. Since you don't know the shape it's in, go over everything. dizzy, check for spark, plugs, firing order, fuel, timing, grounds, anything that might be preventing it from starting.
when you say it does run on starting fluid, does it run fairly well? if its not getting adequate fuel obviously the first place to start is the stupid aftermarket fuel pressure regulator. try finding a thread on installing one of those things properly. or just ditch it and go back to the stock one. whatever you think would be easier, or if you have the stock fpr readily available.
lastly see what info you can get from the friend you purchased it from. granted by the shoddy work he did who knows if he would be much a help but its worth a try. maybe he still has the stock fpr. also install fuses in the fuse box where they are missing. and what ecu are you using btw, just curious