And I don't think that LN is likely going to mend matters here because it won't affect volatility. It is volatility due to Bitcoin's speculative nature that prevents it from being used as a payment method.
It will matter, and in a significant manner as well. It actually surprises me that you don't see that. Currently the next few aspects are what bothers people, and at the same time prevents Bitcoin from becoming a mainstream phenomenon that it deserves to be.
1) high transaction fees.
2) slow confirmation times.
3) low number of transactions that it can process per second.
LN tackles all above annoyances that people 'suffer' from in today's market, and will stimulate people to transact with each other far more than we can imagine right now. In other words, LN is a major adotion booster, that's a fact. Regarding using it as payment to purchase goods and whatnot, I more or less agree that it won't change very much in that aspect. It has partly to do with the volatility, but the main point is that people don't want to spend something that can jump up significantly in value the next day. That's something we have been dealing with for years now.
You didn't come up with anything new that I haven't heard already. The points you list are not what affects volatility as an obstacle to wider adoption. Besides, the way you claim it as an established fact clearly reveals that you don't quite understand what's going on with Bitcoin on a larger scale. LN can make people transact more but it is not an adoption booster. I mean adoption as in real economy, not for speculation purposes. But it is doubtful even for speculation because there are a bunch of top altcoins which don't have these issues and did it boost adoption? In other words, it will mostly be the same people that will transact more, if at all.