Engine hard to turn over.?

Okay I have a 2000 Pontiac Grand Prix SE, 3.8L V6. It has 168,000 miles on it. I left the house and the engine started up rather roughly. I drove about 3.5 miles (engine seemed to run fine) stopped at a store, and when I got back in the car it wouldn't turn over. Replaced the starter, main bearings, rod bearings, timing chain, and soon to change the oil pump. The engine is so tight the starter can't turn it over. There was small metal grit in the oil pan when I changed the bearings, but the old bearings only had what appeared to me to be minor grooves in them that you would expect on a car with over 100k miles on it(also crankshaft didn't have scrapes on it or warped). The MAF sensor was triggering the check engine light before this happened and I had a small oil leak around the valve gasket (oil was not low at time of engine malfunction). When manually turning over the engine with a beaker bar it takes and incredible amount of force and sounds like the compression is abnormally high. Anyone have any thoughts as to the issue? As I am almost to the end of my list of things that could possibly cause this type of issue. (also rods and pistons do not appear to have any abnormal ware or warped)