Welcome to the forum.
I suggest that you ignore that target. I really believe that it is not going to happen if you lose weight in a healthy way. I think that you are setting yourself up for a major disappointment - and major disappointment never helps people in the long run.
I do however think that you can lose a lot of weight in 11 weeks - enough to improve your health.
I do think that you can lose 50 pounds or more.
I do think that you can lose weight in a healthy way.
I know that if people lose weight in an unhealthy way they can damage their bodies which can be very dangerous.
If people lose weight in an unhealthy way they do not really learn the kind of habits that are going to keep them slim and healthy over the long term.
I suspect that you will think that I am not being supportive - but I really do feel for you. I want you to solve this problem and I really believe that removing the 50 pound in 11 weeks target from your head and losing weight by eating in a very healthy way at the right calorie level while exercising will work really well for you.
Think about this - if you lose 30 pounds in 11 weeks and the remaining 20 pounds in another 11 weeks - solving your health issues - should you feel like you have been a success or a failure? I believe that you would have been a success...
I believe that you will be most successful if you celebrate every pound and indeed half pound that you lose along the way and feel proud of every day when you eat healthily and exercise. We tend to do best when we feel good about ourselves.
Eat strictly according to your food plan by all means - but ensure that it is giving you sufficient macro nutrients so that your body works healthily. Use the opportunity to relearn how to build a healthy food plan.
I suggest that you read the following thread - it may help you settle in and make friends
http://weight-loss.fitness.com/threads/57955-My-advice-to-newcomers
Good luck with your project.