Thank you for considering these points. However, note that you chose certain things to talk about, and the set which you chose appears to give a misleading picture.

"I want to appear to people as if I am making a good argument, but they are easily distracted so it's okay if it's more like propaganda" doesn't seem like a position that we should endorse.

Brevity is indeed important, but it is then all the more important to focus on the critical questions that actually support the point rather than bringing up suggestive statistics and letting the reader fill in the details (probably incorrectly!) in their minds.

For instance, if 3% seems small, you might then ask: well, what fraction of people carry guns? Seems like about 1%: https://www.washingtonpost.com/news/wonk/wp/2017/10/19/3-million-americans-carry-loaded-handguns-with-them-every-single-day-study-finds/. So you wouldn't expect the number to be very large...but if 1% of people carry guns, but 20% of mass shootings that are stopped by targets are stopped by a gun...hm...that suddenly seems pretty important.

Is it practical for enough people to carry guns? Or are they already, and mass shootings happen mostly where guns are forbidden? Or something else?

Really, if you're not talking about this stuff in a seven minute chunk, you're not addressing the question of what the right thing to do is. It's fine to give an opinion, but it's also appropriate to get called on an argument-like opinion that looks reasoned but isn't reasoned the way it needs to be.