An ex-marine who lost his arm in Afghanistan has got a custom superhero-like prosthetic replacement – which allows him to lift up to 400 pounds. Cpl. Sebastian Guadalupe Gallegos, 32, came up with the idea of an aluminum and carbon-fiber arm after he broke 15 conventional prosthetic ones. Sebastian had his friend George Schroeder, an engineer, manufacture the custom arm a year and a half ago. Now, Sebastian is able to box, lift weights and even care for his son better. Sebastian, of San Antonio, Texas, USA, said: “It’s the only prosthetic that I can do things with and trust it.” Sebastian is o…