To answer both questions...
1. No, not overpopulated as living standards are rising around the globe rather than declining. The rate of global extreme poverty has been cut in half in about 20 years which is pretty amazing. There is really nothing that suggests we're at some type of critical mass where the earth can't support the population. The only thing you can maybe point to is the prices of commodities continuing to rise over the last few decades.
2. It would be hard to put a number on something like that, but a scenario where the earth could become overpopulated is if the developing world were to continue to develop at a rapid pace and the gains in agriculture, energy, materials, etc were not able to support it. Then you would have intense fights over resources, let's hope we never have to see what that looks like.
Doomsday population scenarios are nothing new, Paul Ehrlich had his book "The Population Bomb" in 1968. He makes a lot of good points in the book but the big variable he got wrong was that he underestimated human ingenuity and the developments that would arise over the next few decades.
And lastly, wtf is with the bold font man? You can't just come with the regular font like the rest of us? What you think you fancy or something?