If the Gatekeeper voted against Harry, JB has a very good reason in his mind.
I don't think Martha was injured in the battle (they were taking special care with her because she had a plaster and walking problems). Would 3 votes will be enough?
Maybe being on fire for a little while isn't that big of a deal for someone on the Senior Council.
Yes, he may have protections on his body that are not obvious to anyone watching him burn. So perhaps the fires damage his suit for instance, but not actually burn him, or at least not to a major degree. Fire resistance +5, perhaps. So he could have been moderately injured, even in pain, but able to cast a vote.