As far as the trigger being pushed forward, is it possible the replaced trigger return spring is heavy enough it feels different from the spring that was in there? A hammer that can be pushed off of full cock is un-safe, and can be caused by poor fit / engagement, or damage to the sear mating surfaces. A good candidate for inspection by a knowledgeable gunsmith. I can't think of any mistake in reassembly that would allow the gun to function normally, with the exception of the trigger being "forced" forward as the hammer falls during single action shooting.
Larry