Is yoga and diet enough?

Kendra • Find your own happiness. Don't do what others expect of you. ~Baby Dust~
I really need to lose weight and have started a diet of 1300 calories a day for the first two months and then 1500 the rest of the time. I drink 54 floz of water a day. I used to be an avid runner. I would run 8 miles a day and then 24 miles on Saturdays. One day I fell down my porch stairs and shattered my knee cap. I never got properly treated because my parents swore up and down it was just bruised but I should've known better. I was crying I was in so much pain every time I stood and the whole area was purple and black for like 4-6 months. The bones would grinds as I walked I could feel and hear the am. It wasn't until I went to the doctor at 18 about it that I found out it was actually completely shattered and that I should've gotten some serious work done and physical therapy. He said it was too late as it had been a year and a half to do anything and that I just needed to try to walk two miles everyday to get it to hurt less. That was the most excruciating thing I've ever done. I could barely walk and stand around at work and I couldn't fully bend my knee. My husband worked hard with me to get it fixed and pushed me hard to keep walking and while it still hurts and aches isn't nearly as bad. But the problem is everytime I do any kind of fitness my knee just murders me. It's part of why I gained so much weight because it hurt too bad to do the intense physical activities I used to do. Running was my favorite. I tried and tried but eventually realized I couldn't do what I used to no matter how hard i tried. Well I started my diet recently and decided to try yoga again and low and behold I can do it and my knee only hurts a little bit. I spend about two hours doing it and then probably another 30 minutes meditating. Is this going to be enough exercise to lose weight? How much more should I do? What about my diet? I'm poor so don't have access to the best foods but I'm trying. What do you suggest. Any advice whatsoever would be great. I've already lost five pounds on the diet I want to lose 100 lbs by the end of the year. An extra 50 by July of 2018. What do you think? Am I doing good?