TDEE? MFP Calorie Recommendations? Newb needs help

I am punching in my information on the TDEE website, and it says the answer is 3,104 calories. I read somewhere that someone said to multiply that with .8 and that would be the calories I need to eat to lose? That would be 2483! That just doesn't seem right. I'm so embarrassed to post this info here because I have never posted it publicly. But, if I don't get help, I am never going to lose the weight, and I figure if anyone out in the cyberworld would understand, the people here would. MFP says I should eat about 1610 calories a day.
39 years old, 5'4", 315 lbs. Sedentary mostly for now, because I am working on food/nutrition, and will gradually add in exercise, but I do walk about 3 days a week for about 30 minutes. I have some health issues - mainly injury from a car accident which affects my back, shoulder, and neck. The other issue I have is that I have a few vitamin deficiencies such as Vitamin D and folic acid. When the Vitamin D is low, I am exhausted, but I do take supplements. I also have sleep apnea.
My goal is to lose as close to 100lbs by next May when my daughter graduates from high school, although I truly want to just get healthy. I cannot describe how embarrassed it feels to go on a field trip with one of my kids and not be able to fit in a seat, or get short of breath trying to climb steps. I also need to teach my children healthier habits, and I can't make them do something I am not willing to do.

The biggest changes I have made so far - more and more organics, more fruit and vegetables, cutting out soda other than an occasional diet Pepsi when I have a relapse (but the last one tasted awful to me!), cutting the majority of sweets (but not denying myself because I know that I would indulge worse if I did), and cutting back on eating fast food. The last one is difficult because we travel a lot during the school year and it's hard to figure out what to eat at McDonald's or Wendy's. But I know its a problem because since we stopped eating out a lot after school let out for break, I lost 10 lbs.

Whatever recommendations you could give would be most appreciated. I see all of your success stories and I am so inspired!