I'm going to suggest a different approach and what is I think a better and more cost effective option.
Ask around and find a good criminal defense attorney in your area who is well versed with self defense law and the use of deadly force by armed citizens. Then meet with that attorney and pay a retainer up front to ensure his services in the event you ever need them.
Unless you look or act shady, he or she is going to view it as a very low probability that you'll ever have need for those services, so the retainer should be pretty small - on the order of $100-$150. On top of the $100-$150 or so you'll pay for the legal consult, you're only going to be out $250-$300 in up front costs.
How does this save you money? Three ways:
1) During this initial meeting your prospective attorney will tell you exactly what to do if you are ever involved in a shoot, and he or she may review the use of deadly force with you. Having that legal advice in advance makes your attorney's job a lot easier and it will often prevent your prosecution.
2) After a shoot, since you followed that advice, didn't talk your head off at the scene and waited for your attorney to arrive, your case will be much less complicated and much easier to defend, which will save you a lot of money you would have otherwise paid in legal fees.
3) instead of paying $150 a year for insurance you'll probably never need, and if needed you may not even benefit from, just bank the money in a savings account. In ten years you'll have $1,500 plus interest that is on tap for legal fees, etc if needed. In 20 years it'll be $3,000 plus interest, and if you never need it, it's still money in the bank.
