It is very likely that there has always been war. Those have been documented even between chimpanzees and those fights absolutely were lethal. https://en.m.wikipedia.org/wiki/Gombe_Chimpanzee_War

Well it would appear you have chosen to redefine war that way. War is generally defined as a state of armed conflict between different countries or different groups. Tribal groups have historically waged small scale wars without large scale agricultural or significant logistical supply lines. Semi nomadic herdsman tribes of the steppes have a rich history of tribal warfare as do nomadic native Americans.

If your points are true then human populations would have exploded at the dawn of the human race due to food abundance and lack of war or any form of lethal encounter. If everything was better back then, why have population exploded and lifespans increasing over the last century.

Famines can be caused by monocultures and short sighted management. Absolutely! However ancient humans did struggle every day and did spend most of their waking hours gathering, preparing, hunting and cooking food whilst avoiding predators and aggressors.

If we "fucked everything up" then why do we have humans in developed countries living longer on average than at any other time in history.

I hate plenty of how the modern world has worked out. We have almost countless problems to deal with but there was no "paradise" back then. Plague, mental illness, cancer, rape, theft and violence cannot all be blamed on agriculture and "institutions". Take infection for example. An infected cut or a tooth absess could kill you back then. I would have been deaf by now due to an ear infection. Members of my family would have died from breast cancer, Type 1 diabetes and epilepsy. Any of us could have drank tainted drinking water and died.

Your last point is confusing. You say we have a lot less mothers dying in childbirth, then you say we didn't for most of recorded history up until a century ago. But we don't live a century ago. We live now. Childbirth is safer now. Therefore your point doesn't really go anywhere. Childbirth in the woods is dangerous, a million things can go wrong. Backsliding? Source required. Show me any evidence that a surgery or childbirth or even drinking water is safer on average back then.

I would be interested in where you get your sources for some of these claims. Ie. Childbirth one and the lack of lethal encounters in ancient peoples. Its a nice idea that there is some nicer world we could all go back to if we destroyed civilization. Reality is unfortunately more complicated.