Actually, if you do the math, there would be room enough for families of four to have an acre of land, room for roads, and with apartments complexes, there would be room for the rest of the infrastructure. However, if not then move them to the midwest, and you would have more room.
The point being, we are NOT overpopulated.
It is not the space, it’s the inability to get along as you alluded to. However, we do NOT need to populate a new planet to survive.
If we cannot get along to survive here, we are not going to get along to survive on another planet.
It is not a space problem we have, it’s a human nature problem that we will always be at war, because there will always be those who want to control us, and those who will agree to become slaves to those who want control them. Against us who want NO ONE to control us.
57 million square miles of land mass on earth. If 8 billion people get 500 sq. feet of space each...I think it works out roughly to the area of calif+Oregon+and washington state.Not including mountains or rivers as habitable.
The rest of the world goes to infrastructure,roads, schools, factories, recreational space ,farming, production of living aids...clothes, sitcoms, etc. More space if some housing was 2 storied buildings.
Then, there is that “mankind is evil” problem...as you mentioned.