Well if your trying to gain that much weight, you definetly need to eat alot. I do not see any actual weight lifting up there... makes me ask what kind of weight are you trying to gain?
Push ups and sit ups will build little strength and can build good endurance, but they are not really going to add any muscle mass.
Work, pushing carts, etc. usually wont build the muscle mass too much either, because your usually lifting around the same amount of weight, and its not like you are working to absolute failure.
If you want to gain that much weight hopefully you want it as muscle, and you will need to familiarize yourself with weight training. Here is a good place to start READ alot of stuff. Good luck!