I wouldn't dare assume what's in someone's head and I try hard not to mischaracterize anyone.

Be honest. You've had dreams/thoughts of killing someone in self defence.

These two statements are conflicting.

I just wanted to know if that person ever dreamed of killing someone,

You could have asked them, but you instead told them how they feel.

I get the impression that some people that want guns for self-defense are 'itching' to kill someone and are using self-defense as an excuse

As I mentioned, those people do exist, but they aren't the norm and conflating them with just a normal dude who doesn't want to use it but will if forced won't make you friends with those normal people.

I read that a girl got shot because her basketball landed in someone's yard and the person killed her.

Which isn't legal. Maybe in Texas idk about them, but in most of the country that'll buy you some prison time unless it landed in your living room and she kicked your door in to get it back.

without proper healthcare, including mental health, having the right to use a gun for self-defense is a recipe for disaster.

For you maybe. I'm fine, and for all I know so is that other person you first replied to. Not that those things wouldn't be cool, but the need for them does not invalidate the need to defend oneself. In fact, the fact that we don't have those may well contribute to why we do sometimes need to defend ourselves, tbh. In the meantime the best you can do is evaluate that for yourself, if you can be safe and use it only when you have to, great. If you doubt your ability, making the decision to not have one is a good one and I couldn't fault you.

Plus, the 'stand your ground' laws seemed deeply flawed, though this is coming from a Canadian that doesn't have the right to use deadly force to defend my property.

Neither do Americans with SYG nor Castle Doctrine. Castle Doctrine says you have no "duty to retreat" in your home or vehicle, meaning if someone breaks in while you're inside, you do not have to run away before responding to the threat. Stand Your Ground extends this to any place you are legally occupying. That said you still have to abide by all other laws at the time, including but not limited to "deadly force is only legal to use in defense or prevention of death or great bodily injury." Not "property."