
No, buddha isn't the reason humans have the valkyrie weapons. The valkyrie weapons are the 13 valkyrie sisters that turned into weapons to assist humans. Buddha is the only one who doesn't use a valkyrie weapons since he has his own. Everytime a human loses a valkyrie sister dies, and so the remaining valkyrie sisters will appear soon in battle

No I think his powers is the one that binds a valkyrie to a human. I forgot what chapter that is, but it is when loki and bishamonten found out buddha was a traitor. Volund doesn't exist in mythology I think, it was buddha's powers that turned valkyries into weapons and made them resonate with humans. That's why Brunhilde and Buddha made a deal in a chapter somewhere, and Brunhilde knew it would happen bc Buddha is... well Buddha.
Ngl I was hoping that Zero would do something fatal to buddha, cause then it would be more cool. If buddha wins as expected by almost everyone then it would be a bit more boring