You're right. We gotta push for Global Universal Basic Income. Someone surely has "X% of people live on less than 5 dollars a day" stats available on hand. If it makes their lives better over there, they have less incentive to uproot their life to go over here.
What's the cost and how much I'd need to pay?
Not sure if sarcasm or serious...
No - rich Nordic countries have an obligation to open borders due to their wealth, relative privilege and the climate emergency that will push everyone up northward into these countries