oil pressure !!plz help

[180sx]

ok guyz plz help if you can!!! ka24e 207k on it oil pressure light is on and engine won't rev past 3000 rpm also entire engine sounds so loud mostly chain and valves. took oil pump off(there is two holes)took a hose stuck it into a bigger hole blew into it oil bubles in the pan.sucked it oil comes into the hose, other hole when i blow nothing happensn air won't go anywhere, but i guess its normal cus only oil under pressure can go through that hole. i also took pump off drained oil from it stuck it back in started the car for few minutes, took pump back out and its dry not a drip of oil was in it.so i figure my pump isn't sucking oil what do u guyz think??? if it is the oil pump is it rebuildable?what else shoul i check or how can i check the pump:help :help

[quiksilvia]

how was no oil on it if its in oil?