This is indisputably a fascinating and brilliantly-argued article — but three sentences from the end you discredit everything you said: “ Fear of another World War nearly stopped World War 2, but didn’t.”
Actually, throughout the 1930’s, fear of another World War was the direct cause of World War 2. The constant threat that if the democracies would not back down before Hitler then there would be a war, and the democracies’ capitulation to that threat, created the conditions that made World War 2 happen.
Had Britain and France not been so terrified of war against Germany; had Czechoslovakia not been frightened of confronting the Wehrmacht in 1938, and again in 1939; had Neville Chamberlain understood that the threat of war was less frightening than the threat of an unrestrained Hitler leading an unrestrained Nazi Germany —
— then quite conceivably the Second World War would not have happened.
Similarly Brexit. It is uncontested among historians that the First World War was an all-but-inevitable result of what you have called here “the web of treaties across Europe”. (And throw the USA, China, and Japan into the mix for good measure.)
If you accept that (and you seem to), then the obvious conclusion is that weakening treaties makes war less likely, not more. Hence Brexit, an isolationist USA, and dismantling (or at least weakening) Nato, actually avoids the scenario that led to World War 1.
Maybe — just maybe — Trump and Brexit have together made the world much, much safer.