Won't explain the back firing or hard start. Check your cam timing again and be sure your valves are adjusted correctly, with the correct push rods and rockers arms. After re-aligning your cam timing, check the valves on #1 cylinder to make sure they are both closed in the compression stroke. If the valves are not closed, check your crank key and cam pin to make sure they are not sheered and giving a false alignment.
And beware, if the cam timing was off, you could have bent valves and/or damaged pistons.