Have you ever considered speaking to a personal trainer? Someone very knowledgeable in this field that can give you straight facts on how you're doing in terms of exercise? And someone that can specifically target any areas that you are extremely worried about? I think you would really benefit from this. Even just getting a gym membership and speaking to someone there and getting some facts straight. Exercise videos come in ALL varieties. Some of them are a bit easier for those that can't do intense work outs, but others can be EXTREMELY high in how many calories it helps you burn. An aerobic type video would focus more on the calorie burning and stamina building and the like. One that focuses on stretches and other exercises would be towards toning the body and building muscles, at least that's what I would say. Have you read the description on the box of the exercise tape? Does it mention anything about what the goal is for someone that uses it? Just a thought.
In terms of not eating enough. The worst thing you can do right now is lower your food intake, and exercise too much. Exercise requires energy, which comes from food. You can't burn away everything on your body, and the first thing to go when you're hungry is muscle. Muscle may weigh more than fat, but it gives you a good shape and tones the body as well. It would also help you in terms of swimming if you ever wish to go back! :).
I wish I knew more about this. I think you're doing too much, to be honest. Let's say you do get 1000 calories per day (even though you said only 800). You should probably be getting about double this amount (maybe even more). You have ALOT of room...
And as a final note, do you know why you are so conscious of your size or eating? Is it for health reasons, is it for appearance reasons? Because for both of those, eating a healthy diet (with balanced nutrients and enough calories) will make BOTH those areas a lot better.
In terms of running, that's not something you should be doing daily. It can get very hard on your knees (make sure you have very good shoes!). If you don't like running, I would really recommend doing it maybe 3 times a week. You don't need to do it daily. In terms of your exercise videos, if they are aerobic workouts, then that's your cardio, and you don't quite need the running to support you in that area. If they are more exercised base, targetting toning areas of your body, then you may want to alternate with some kind of cardio (something that gets your heart rate up) such as running, biking, etc.
And like I said, I think that for you, having someone with knowledge explain how things work is very important. Having someone VERY knowledgeable in an area giving you facts about how to stay healthy and look good, and someone that can tell you what exercises you can do to keep youself looking and feeling the way you want, might help you. A personal trainer can assess YOU specifically, because not everyone is the same. Or if you can't do that, even talking to someone that knows about exercises, or looking up online how many calories you burn per work out (or during a specific work out). It may vary from person to person, but it can help.
And as a final note... weight is just a number. Muscle weighs MORE than fat. Make sure you know this... because even if you do gain something like 5 pains in terms of number, you could actually be slimmer, or just more toned.
Either way, best of luck. I wish I knew more about this area, but hopefully you can talk to someone that does :). Like I said, I think you're overexercising, and you might hurt your body in the long run. I would drop down how much you're doing at the moment, or at least alternate execises as well.