From what you say, I would suspect something is jamming the crank if it won't turn over in either direction with a breaker bar...
If you had fluid in a cylinder (hydro-lock), you should be able to back the crank up...
Same with something physically in the cylinder (bolt, valve, etc...), you would be able to turn the crank backwards...
If you can't turn the crank over in either direction, something is physically jamming it... Especially if you just were able to turn it over by hand and with the starter....
