Almost no oil pressure help

Removing the oil filter and spinning the engine over like Del recommended is a good idea. You already have seen some thick sludge come out of the oil gallery. If there is more and it is stopped up, that could be your issue. You also might try applying air pressure to both the gauge gallery and the supply and return ports on the filter boss on the block. You might blow whatever it is out. Of course, there is always the risk of sucking it back up, but I think that would be minimal. It's worth a try as it costs nothing.