The situation is complicated and I suspect you understand that as well as anyone. Only your point 7 is a strong one: it is none of our business who runs Syria as it is a sovereign nation that is not threatening us or even our regional allies. Your point 5 is weaker than wet tissue paper. You say there is no evidence the gas attack was not a false flag operation, but where is the actual evidence it was? You don’t have it. What if it turns out the Assad regime did use poison gas on civilians?
What should make us question the US strike is not the simplicity but rather the complexity of the Syrian situation. We have many actors acting overtly and covertly. Much of what is actually happening does not fit into your cartoon level conspiracy. You seem to have ignored the Kurds in your analysis, and what a mess might ensue if Kurds play a major role taking Raqqa. You don’t say anything about Turkey and Erdogan, but no solution will work if the Turks undermine it. The burgeoning ties between Israel and Russia that allows Israel freedom of action to cross Syrian airspace against Hezbollah contradicts your central thesis. You don’t talk about the larger Iranian vs Saudi battle for strategic influence nor the question of whether the Iranian theocracy and the Syrian secular regime can maintain an alliance in the long run. Once ISIS is defeated, will that help or hurt the Al Nusra controlled rebels?
It really is complicated and the US under Bush and Obama made a mess of similar regime-change situations. Trump has not announced or built support for any strategy and it’s not clear he has one yet. It’s better to figure that out before we jump into a complex struggle and blunder our way to WWIII.