Max, you speak of human suffering as if it is something that can be controlled. Human and animal suffering is a part of life. A zebra being mauled by a lion, thats suffering, a single mother with two jobs raising a family, that's suffering. Sure some suffering is bad, but others is absolutely great and it molds our characters. I would not be the man I am today if I did not suffer and overcome my own problems. Suffering gives us the ability to make our lives better, and have a sense of personal pride.
Your argument actually seems to contradict itself quite a bit and if you study philosophy, you will see that this whole population argument has already been put to rest. The reason is that if we went along with your purported views to lower the world population to a "stable" number, how long before people begin getting pissed and begin to suffer because they can only have a set number of kids. If I was told I could only have 2 kids to replace me and my wife, I would suffer as a result. You are missing a huge point that people suffer when they are told what to do. People want and should want to live their own lives and make their own decisions. Driving this point home, there will never be an end to all human suffering, and there really shouldnt be, suffering makes us human.
Also, if we lower the population by none other than murder, that would cause plenty of suffering. And if we did achieve a lower population by murder, how long till we have to murder people again and lower the population once more?
If you look at the current fertility rates, you will see that we already are a dying race. Our epigenetics are all screwed up and every generation gets worse and worse. Basically what effects you will effect your grand kids and so forth. Doris Rapp, the world's leading pediatrician studies soy formula and its effects on young infants. Soy formula and other estrogenic substances fed to babies are not only causing our young men to go into andropause earlier, but also making men homosexual. Japan needs over 100,000 in vitro fertilizations every year just to have kids. Other countries are just as bad. I live in the US and am well educated of the birth rate. The US birth rate is currently 1.9, which is not enough to replace ourselves. Combine this with the fact that 15-25% of these births were of illegal immigrants, and counted in studies as legal US citizens as per the 14th ammendment, you will see that we are in a birth rate/fertility shithole. Check out the information the CIA currently has on population, the birth rates of higher income nations are lowering. It seems that the higher income nations are in trouble and will be replaced by individuals from lower income nations.