Joe;
12 to 15 lbs. seems low to me,so is your 600 rpm idle. Try turning your idle up to around 800 to 900rpms and see what the pressure is,should go up some,say maybe to 20 to 25 and that would be o-k,seems on a "fresh" motor
oil pressure should be more than that.....
Cold idle pressure is good and hot at 2000 rpms is o-k but seems a little low,seems you should have at least 50psi at 2000 rpms especially with a fresh motor..........
David