The problem with umbrella tort insurance policies is that they, like most insurance, will not cover intentional acts. It's like malpractice insurance - if you can show that what you did was a tragic but unintended consequence of trying to follow all the best practices (the Four Rules in this case, mostly) then you may be covered. But you will never get coverage for anything related to intentionally shooting the BG. So what you are buying is coverage for that stray bullet, with no guarantee that you actually will be covered in most of the situations you might encounter.
There are several outfits that sell membership in a legal services scheme - you buy a "policy" that promises to get you an attorney if you are arrested who will deal with the arrest issues, and then a referral to a criminal defense attorney who may have offered "special rates" to policy holders - in spite of the fact that price fixing is a violation of the Canon of Ethics. In today's housing market there might not be enough equity in your home, your parents' home, and your grandparents' homes to cover the cost of something like the Dream Team OJ Simpson had. All you can be sure of is that you can get the best legal representation you can afford.
All that being said, it helps to remember that most of the time we should be facing a trial in which we go in pleading guilty! "Yep, I shot that sucker. Meant to stop him in his tracks, and his dying sure made sure my goal was reached. Of course, I'm also claiming that my killing him is excusable under the circumstances, and that me killing him was justified based on his actions." (Folks seem to forget that most of the time.)
stay safe.