I find that safejumping Deejay really helps Ken with this matchup, it’s much better and more effective than crossups, followed by throw / SRK / sweep mixups. And if you’ve got O.Ken, you can install an invincible SRK to beat the Jackknife or MGU. It’s tough to get the timing down, but I’m pretty confident about it now, and it totally throws the DJ player off his game.
ST Wiki says DJ’s RH Jackknife hits on the 5th frame but I thought it was the same as Chun Li’s RH Tenshou, which hits on the 3rd frame. If that’s right then that would explain why I find it easier to safejump DJ than Chun Li, so maybe the Wiki is right.