> 3) When the speed at wich the atoms gets near the speed of light they will get heavier

They don't, but the overall mass of the object increases as its energy content increases.

In principle this would be possible, but no material can get anywhere close to the temperature it would need without flying apart. To avoid that, you could try to heat it extremely quickly - have a giant array of (to be developed) gamma ray lasers all focused on the same spot. But if you can do that then you can skip the target - the light pulses alone will be sufficient to make a black hole (kugelblitz.