I'm curious how many times someone avoided injury or death because they used a gun in self defense.

Kind of hard question to answer. But the Obama administration commissioned a report from the CDC on this topic.

http://www.nap.edu/openbook.php?record_id=18319&page=R1

Slate had summarized the main points and I think this is the one most relevant to that question:

Almost all national survey estimates indicate that defensive gun uses by victims are at least as common as offensive uses by criminals, with estimates of annual uses ranging from about 500,000 to more than 3 million per year … in the context of about 300,000 violent crimes involving firearms in 2008,” says the report. The three million figure is probably high, “based on an extrapolation from a small number of responses taken from more than 19 national surveys.” But a much lower estimate of 108,000 also seems fishy, “because respondents were not asked specifically about defensive gun use.” Furthermore, “Studies that directly assessed the effect of actual defensive uses of guns (i.e., incidents in which a gun was 'used' by the crime victim in the sense of attacking or threatening an offender) have found consistently lower injury rates among gun-using crime victims compared with victims who used other self-protective strategies.

Unfortunately, we don't know the answers to these questions because the research to uncover them is continually blocked by pro-gun lawmakers.

This is just a BS talking point. There is plenty of research.

This modern day assumption however, like the 2nd Amendment, sounds entirely outdated in the face of modern military.

You do remember that our wars in the middle east have been quagmires and have been primarily fought with small arms and IEDs, right? I am sure you think everyone would go home by Christmas the US military is so good.

If I do not have the freedom to lawfully kill someone with the ease and efficiency of a firearm, I am not truly free.

I am assuming this is your own phrasing. No I don't agree. The point is that it is effective defense weapon not that I want to go around killing people with ease.

If someone can sympathize with that statement, I imagine they will never be truly free.

Well I don't agree with that sentiment. It explains much about those who are afraid of firearms and 2nd amendment rights.