Check out the companies making the biggest moves midday: Miami International Holdings — The parent of Miami-based exchange operator MIAX surged more than 43% in its public market debut at the New York Stock Exchange. The company priced its IPO at $23 per share. It last traded above $31. Paramount Skydance — The media company fell more than 6%, giving back some of Wednesday's stunning surge. Paramount rallied 37% in the previous session, marking its best day ever. Amcor — The packaging company plummeted more than 14% after its fiscal fourth-quarter results missed analyst estimates. The company earned 20 cents...