You can be sued for pretty much anything providing there are no laws to the contrary. In my state, whether or not you choose to use quality SD ammo (read that as effective expanding rounds or hollow point if you'd rather), make modifications to your trigger, use night sights, or anything else of the type is not going to be an issue in a criminal trial. As a lawyer knowledgeable in these areas once told me, the 800 pound gorilla in the room is going to be whether or not your actions were excusable.
In Virginia, we have what is known as an affirmative defense. Your attorney is going to put you on the stand and ask you, "Mr. Smith, did you shoot Mr. Jones?" to which you'll respond, "Yes sir, I did". He is then going to ask, "Under the same set of circumstances, would you do so again?" to which you would reply, "Yes sir, I would". This is going to make a zealous prosecutor's task to show negligence or anything of the sort pretty darned hard since you just admitted that you did what you did deliberately and would do it again.
Now IF the perp or his family try to sue, they are going to have a very hard uphill battle on their hands to prove you are somehow at fault for the his actions. I have asked a county sheriff candidate and a commonwealth's attorney if they see many cases of law suits filed against someone who was judged to have acted within the scope of the law and both said it was very rare in Virginia. Yes, it can happen, but not very likely or common place.
As far as ammunition is concerned, use the best you can find and afford. Do your research, stay current, and apply some good common sense. And for God's sake, don't listen to people who obviously don't know what they're talking about or are so full of crap they hardly know which end the rounds comes out of. Read, learn, research, and pay attention to those who can offer valuable information. Making a mistake with the choice of SD ammunition or if the time comes when you must use it could cost you more than money. It could cost your life or your freedom.