Steel body constitution and Chainsaw Staff Sword are the weapons Xavier formed for himself. He originally wanted to recreate his divine body from reality, but his belief wasn't strong enough, so he had to settle for this form suitable for duels.
As for the steam emanating from the Chainsaw Staff Sword, it's not for aesthetic effects, but the divinity he has manifested.
Honor duels do not prohibit titles, nor do they prohibit divinity.
If not for the Power that forms honor duels, involving order accessible only by the pinnacle of lower-level Gods, Xavier wouldn't be forcibly drawn into the Holy Land just relying on his inner divinity.
In his view, the remaining divinity inside him is his trump card to defeat Wu Chang, the violator.
While in Wu Chang's view, it's fair that Xavier keeps his divinity and Wu Chang keeps the title "Blasphemer".
