The pilot reported that the landing approach was uneventful up to the flare and touchdown. He increased engine power just prior to landing because he thought the airplane was slow. He rounded-out and flared higher than normal, and then the airplane "hit hard" on all three landing gear. The airplane began to porpoise between the nose and main landing gear, but eventually settled onto all three landing gear. The airplane then made an uncommanded left swerve that the pilot was unable to counteract. The nose landing gear separated from the airplane when the airplane nose impacted a non-breakaway steel runway light. The airplane then nosed over in the grass easement off the left side of the runway. The cabin roof, engine firewall, rudder, and vertical stabilizer were substantially damaged. The pilot was seriously injured with a broken neck. The airplane was not equipped with shoulder harnesses.