at 300lb your problem is definitely the weight more than strength.. it's good that you set a lofty goal for your weight loss, but don't be discouraged if you don't reach it. your goal is 95 lb in 6 mo, which is about 4lb a week.. that's pretty intense.. you'd need to be at about a 750 cal daily deficit.. that's pretty tough, especially to maintain for such an extended period of time. drastic weight loss is absolutely necessary to improve your physical ability in those three tasks, though. it takes a ridiculous amount of energy to move 300lb around. even jumping rope, like how stern suggested (and it's a great excercise), would likely be too exhausting... gravitational pot. energy = m*g*h, you're literally using 50% more energy to jump than a 200lb man.. same goes for running, pushups, situps, etc. that 50% is huge. i doubt i could jump rope for 15 seconds if i were wearing a 100lb jacket.. i doubt i could run/walk far either. you gotta lose that weight, top priority, but, again, don't get discouraged if you don't meet your very high goal.
weight loss happens primarily through nutrition, especially a man your size, you're already burning plenty calories just walking around. there are enough credited sources for dieting tips on the web that i won't waste time repeating what they wrote (in better english), but seriously, i can't stress enough, if you want to improve in those three tasks, lose the weight, and aim to do so through nutrition. keep a keen eye out for caloric content and make no exceptions in your diet.
in the meanwhile, to improve in those bodyweight excercises without yet being able to do them, consider (i) benching for pushups, (ii) plank excercises for situps [look into beginner's yoga sites/dvds], (iii) lower-body stationary cardio machines (bikes, stairs) to increase endurance for the 2mi.
it's definitely possible but it's gonna be tough, 6mo is not long in the world of fitness, best of luck
weight loss happens primarily through nutrition, especially a man your size, you're already burning plenty calories just walking around. there are enough credited sources for dieting tips on the web that i won't waste time repeating what they wrote (in better english), but seriously, i can't stress enough, if you want to improve in those three tasks, lose the weight, and aim to do so through nutrition. keep a keen eye out for caloric content and make no exceptions in your diet.
in the meanwhile, to improve in those bodyweight excercises without yet being able to do them, consider (i) benching for pushups, (ii) plank excercises for situps [look into beginner's yoga sites/dvds], (iii) lower-body stationary cardio machines (bikes, stairs) to increase endurance for the 2mi.
it's definitely possible but it's gonna be tough, 6mo is not long in the world of fitness, best of luck