Hmm... the measures I would use to help with weight loss depend on weight, and in my own experience my guesses of weight have been wildly inaccurate. I would suggest finding a reliable scale and weighing yourself- even if you don't like it, it's the only way that you're going to be able to use anything I can help you with. (I've done the "just eat healthy, try to exercise" approach and it really hasn't worked for me)
(Using this website to calculate your BMR, maintenance calorie allowance, and then reducing by 500 for a pound a week weight loss- you can reduce by 1000 for 2 pounds, but for most people that's probably not terribly feasible)
Whether the amount of exercise you do is right for you depends on your calorie needs and intake- if you're eating less than you're burning you'll lose weight, it's as simple as that (except you need to be healthy and you should never go under 1200 calories a day or 1000 calories under your maintenance amount). Theoretically, you don't need to do any exercise to lose weight, but I wouldn't recommend that approach (a, you'll be hungry all the time because your calorie allowance will be really low, b, it's not good for you in the long run).
I don't know what the 100 workout is, but you need to get your heartrate above normal walking pace- so during that walk, walk briskly.
If you join a gym, see if you can get them to set up a personalised program for you. I did at mine, and it's given me focus and motivation, as well as doing what I want it to do (which is really hard to work out on your own).
