In some episodes of Fullmetal Alchemist, Alphonse gets really hurt. But as long as the blood seal isn't broken, he will be fine. So, in theory, If I tear up each piece of the armor that houses Alphonse, but don't touch the blood seal, will he be safe?
That's right. If you look at Barry and the Slicer Brothers the older bother was nothing but a head before Lust smashed his seal. Barry was completely broken, but only died when the flames burned his seal.
In Fullmetal Alchemist Brotherhood Barry has a bigger role and helps Ed. In the end all that's left of him is one piece of metal that his seal is on, and he is still able to talk though it. He only dies when his body scratches the seal off.