You are correct - there are so many factors to consider, and I am by no means an expert and would definitely accept being wrong in any given area. The general advice that I can give, that will probably keep a person healthier than not, is to exercise, eat well, and not sit for too long. This goes beyond just DVTs - this is advice for living long in general. :) Even outside of clots, sitting is shown to severely cut back the benefits of exercise (although like all studies, this should be taken with a grain of salt as well). 66 percent of studies are wrong, as they say. The reverse advice goes as well - you should not stand all the time either - this is shown to have adverse effects as well.
And as a minor additional note - my 1-3 miles of walking tends more often towards the low end of that range (especially when I am in a rush to get work done), although I do randomly take longer walks (sometimes as far as 5 miles).
There's a lot and that's why seeing a doctor is so very important. I am actually having an anxiety attack right now after reading your post. You didn't cause it :) but it certainly did stir up some stuff with my anxiety.
For an anxiety sufferer like ourselves. It can be very hard. I have numbness in my left hand, an odd pain in my back and shortness of breadth. This could be a lot of things. Things I'd rather everybody not mention because I know them well. But if I went to the ER every time these things popped up well at one time in my life I'd live there. The probability suggests that I am fine. The probability suggests that after thousands of trials similar to this of which I ended up fine, I will likely be fine here. There's a chance I will not be but it's a chance I need to take.
I get so many symptoms on and off (which include numbness, aches, shortness of breath, chest pain). The way I bring myself to relax about these things is that I don't worry about them unless they persist for a particularly long time without any breaks in their occurrence. I actually expressed similar sentiments just now in another comment about the pitfalls of worrying too much.
And as a minor additional note - my 1-3 miles of walking tends more often towards the low end of that range (especially when I am in a rush to get work done), although I do randomly take longer walks (sometimes as far as 5 miles).