The science of the ideal weight

Yesterday during my workout I was thinking about running again. But I have doubts that maybe with this much extra weight I'm carrying now it wouldn't be the best idea to start at the moment. I checked out some running schedules a couple days ago and looked for any advice for overweight people. Hardly found any but I read an interview with Sarolta Monspart where she said her training schedule would be optimal for anyone who's maximum 15% overweight.

Okay, here comes my second problem. When I started to have weight issues I was only 16 years old so I cannot compare my ideal weight to those times. I set 66kg / 145lbs as a goal only because two years ago when I lost weight that was the lowest I reached and I felt good at that point. And of course I had to name this blog something. (: Anyway, I googled some weight calculators just to have some aspect in this topic.

Fitness Online calculates with frame size, current weight, gender, age and height. But according to the manual I think my frame size is right between middle and small. So with small frame size my 'ideal weight range' is between 123 and 136, with medium frame size between 133 and 147. calculates with age, gender, height and weight. According to this site my 'ideal weight' is exactly 145.

Health Status says (based on gender and height) that my ideal is supposed to be 143, but the recommended weight range is between 127 and 159.

Health Central (variables are frame size, height, weight) says with the option small frame size that the ideal weight range for me is 138 - 151.8. With the option medium frame size it's 148 - 162.8.

As a comparison, my current BMI is 27.5 (overweight), the goal BMI (for 145lbs) is 22.7. (normal weight)

So as a conclusion I may say that 145 is reasonable in my case. Somehow I think my ideal weight (not theoretically but from previous experience) is below that. But, don't forget the reason I started this whole calculation thing:
if I say that my ideal weight is 145, that means 15% overweight is 166.76 lbs. Right now compared to 145 I'm 21% overweight.

It may sound weird that I calculated so much for something but I used to run and I'm still reading a lot about running. I'm not afraid of my legs, I just want to be careful with my knees. I spent so many time without exercise and I don't want to make a big mistake. Am I too strict to myself?

Note: I don't give a damn about the scale numbers actually, I just want to feel good and comfortable in my own skin.