When you say the sludge trap was totally blocked, was it blocked beyond the end of the sludge trap itself i.e. did you have to poke crud out the crankshaft as well as the sludge trap tube? The big-end oil passage is over an inch beyond the top of the sludge trap, so the build-up has to go a long way beyond the sludge trap to affect the big-end. I have, in the past, blown compressed (mixed with flushing oil and with the sludge trap removed) into the end of the crankshaft to clear out any bits of debris. DO NOT blow into the sludge trap hole as you will drive loosened crud back up into the oil passages. After refitting the sludge trap blow compessed air into the end of the crankshaft again. The only place it can come out now is the big-end feed however...I have discovered that the oil sludge trap was totally blocked
...has the big-end given any indication of problems? If not, I get the feeling that you are getting diverted down a blind alley (both literally and metaphorically). The fundamental issue is your oil circulation.
With all the kicking and running of the engine, has the oil tank level gone down and, when you removed the sump plate, did much oil come out? If so the oil feed side is working and the problem lies in the oil return side so you need to isolate where this problem resides.
1) Start by disconnecting the lower oil pipe at the back of the cam chest and blow air up the pipe. If the air doesn't come out from the pipe in the oil tank mouth then there is a blockage between these two points (a leak isn't an issue).
2) Check the pump is working as per Paul Jameson's post (wear eye protection).
3) If the pump works, the problem lies with the tube from the sump to the back of the pump which is either blocked or leaking.
Pete
If your using Windows then MSPaint can be used to add arrows, lines and simple text however just a photo of the part you discussing always helps.