Where does it say the Lord will have His share, even if He has to take the young ones?
This statement and the idea that it presents are not found in the Bible. I can't even come up with a twisting of some passage to arrive at this idea. I also did an Internet search to see if I could find a source for the statement and found nothing.
The main flaw is that everything already belongs to God. "Behold, all souls are Mine; the soul of the father as well as the soul of the son is Mine. The soul who sins will die" (Ezekiel 18:4). God does not need to take people's lives for them to be His.
Nor is there a concept that God and Satan are dividing the world's people between them. Rather, the Bible teaches that Satan is going to be destroyed and anyone who follows him will also be destroyed. This is not a victory for Satan but a loss. "Then He will also say to those on His left, 'Depart from Me, accursed ones, into the eternal fire which has been prepared for the devil and his angels'" (Matthew 25:41).