It looks great mate, if you have the time to do, cause it looks like you need a lot of time. You can switch to slow jogging and gradually increase the intensity which will dramatically improve your cardiovascular system, something that walking cannot give you. Try to do other exercises as well, not only pushups. Go for abs(have a mat with you), lunges, burpees, star jumps, tuck jumps and you will be consuming double the calories and you'll b working most of your muscle groups this way. Finish off with pull ups when you get home. Make sure that you eat at least 1000 calories more than your BMR and you'll b fine.