I am an avid runner. I run an average of 5 miles per day, or 5 days a week.
The T25 is a great workout. Keep doing it, and keep eating correctly. I can't stress enough how important what you're eating is.
The next thing I would say is ASICS ASICS ASICS ASICS ASICS. Disregard anything you hear about anything else. Real Runners mainly wear Asics, unless there is a specific reason why they don't. Find a man that runs 20+ miles per week and he will likely have a pair of Asics on. Order them online to fit your foot. Use their easy to use system to do it. It's a great process and ordering new shoes every3 months (half year or more for you probably) keeps you into running. The system they use is recommended by lots of informed runners.
Next, I will give you some advice people losing large amounts of weight need to focus on.
DO NOT JUST RUN. I will almost guarantee if you are losing 50-80 lbs or more, and you don't lift weights/muscle exercise, you will likely put it all back on, PLUS some. And if you do, you will replace the space muscle used to be with fat. I've seen this so many times with adults and students I work with. Lifting weights is extremely good for losing weight, as it burns calories in ways running won't. You will literally burn calories while you're sitting on the couch. Incorporating weight lifting into your routine will all but guarantee you WILL NOT put that weight back on. You will also feel a new meaning to "in shape" with the weights. The T25 is great, don't get me wrong. But eventually, work out your shape with free weight IF YOU CAN. That T-25 exercise will help tighten you lose skin as well, so do a little of everything if possible.
That's my advice, and some of this I do for a living.