For mounting the sword... specifcally the sheath or scabbard. That is tough unless the sheath is a perm mount. Being the molding/casting man you are... you could create 2 small (thinking 2 inch) housings that the sheath slides into, with rubber trim to keep it from sliding out, and mount those to the armor.
My expierience with the "baldrick" style sword sheath is effectively drawing the weapon, especially with limited range of motion.
This is a daunting task you have before you. Luck is wished in your general direction.
Question: Unless you plan on drawing the sword, would you be able to make a mold/cast of the sword housed, and mount the static prop to the armor? I've watched your vids... I think you could.