2) I don't think the House or Senate has to be in their own chamber to due their duties tonight. While those places are being swept and deoderized, there are surely rooms in the House or Senate office buildings, across the street from the Capitol, connected by tunnels, where they can meet.
1) This crowd at the capitol today is small compared to the number who had Thanksgiving, Xmas, or New Years with big bunches of people, but with all cross-traffic, the mingling, no masks, no distance, maybe some yelling, the surge in Corona among the people who were there and everyone they meet in the coming 10 or more days will be enormous. And apparently they came in flights from many different cities. Another superspreader event, by people who don't understand the American system and don't understand disease transmission or mathematics either.