take off the sender wire turn ign to on, it should be 0, earth sender wire and check it should be hard over on high, it could be thermostat or the sender unit, 3/4 in heavy traffic stop go sounds pretty normal but you would expect it to drop when cruising, you need to check the thermostat operation in pot of boiling water, replace it if its been in there while not expensive. Acceleration problems no clue take it to a professional I am not psychic.