Jacob Hammond

So i have a 2000 chevy impala 3.4L OHV V6 front wheel drive at 170000 miles. I bought this car 6 months ago from a family member for 1500 dollars. It had no problems when i first got it, but a few months later i started having overheating problems. I constantly had to refill the water resevoir every few miles because the water was leaking out so fast. I didnt have the money to afford maintainance so i kept filling it up and let it sit for a few minutes for it to cool. I did this for a while then i started hearing a noise everytime i pressed the gas. Thats the only time i heard it. It wasnt a harsh rattling or crunching noise. The only way i could really explain it is the way a diesel sounded. Like a muffled diesel sound. What im thinking is it was one of the pistons making the noise but im not a mechanic or know that much about cars so i cant be completely sure. it did this for a bit and i was scared to drive around because i thought it was goig to kill my car but i still drove it around to work and back. the noise came and went. I was driving on a bridge one day and it started again and my car died all of a sudden and i just let it coast until it stopped and i tried to restart the car and it worked barely only when i pressed the gas a little bit. After that it just didnt work anymore, so we pushed it down the bridge and off the way of cars. I got it towed back to my house (also the power steering didnt work). I tried to start it but it only gave a rough turn. My dad and my neighbor worked on cars so i asked them what was wrong and they didnt really know. They thought i could have jumped time and we just left it to that. I didnt do much for a while and then me and my dad started taking the engine apart to see what we could find. I knew i was leaking at either the head gaskets or intake manifold because i saw a video of a guy with the same leak as me. We took it all apart all the way down to where we couldnt go any further unless we had a cherry picker. I rented a harmonic balance puller to get the pulley bolts off. and we took off all the spark plugs, the timing chain, the valve rods and the rocker arms. I bought all the gaskets i needed to because i only thought i had to replace the gaskets but my dad turned the crankshaft pulley by hand and it would rotate almost 360° hen stopped. We went the opppsite direction and stopped almost 360°. Thats where im at now and have no clue what to think or do.my dad says the pully is supposed to turn freely and not stop so he thinks its a broken or cracked piston or connecting rod but i read online that it could be a valve stuck open. Can someone give me any info