I watched the President’s 11/8/2018 press conference where, out of the blue, he asked a stunned Pence if he’d run with him again? Pence says yes. Way before Miller. https://www.youtube.com/watch?v=gdeZQ4UPup8 I remember when President Trump asked VP Pence if he'd be his running mate for 2020 at that press conference, but I didn't recall Pence being stunned. I remembered him laughing as he accepted.
Your clip doesn't show Pence at all. I found this video of the entire press conference. It shows Pence, mostly from the back and side (as he turned his head slightly), and he does look like he's grinning and laughing. Starting about the 39:15 mark where the reporter asks the question.
https://www.youtube.com/watch?v=6Ysro4Sbd78