I agree. Someone sold this car knowing it had an issue, and the OP was screwed over by a non-Porsche dealer.Picture in post 6 shows not just scoring streaks but pits. That indicates corrosion, probably water or coolant in the engine, followed by sitting for a long time. Could be a flood salvage car that wasn't officially totalled so as to keep the title clean, or the engine was from a flood salvaged car.
Either way OP got royally screwed by this dealer. Pay an experienced, expert mechanic to make a detailed inspection and report, then take that to the dealer with a promise to lawyer up if he doesn't make this right.
I'm not much for hiring attorneys but there might be recourse here. Otherwise I would find a good engine from a wrecked car as someone else suggested. A new engine from the factory makes no sense here unless you plan to keep the car forever and see value in it.