BTW you should record the setup as AI and try to block as Superman. I think your timing with the J2 is a bit too late. If you just hold back Supes will walk back a little and it won't cross-up. You should jump in faster on characters with larger hitboxes.
Ok here are a couple of videos:
After the knockdown if you just wait a moment then do an empty jump in, all the wakeups will whiff. I recorded the setup, and let the AI do it, and I tried to wake-up as Superman:
They have to reeeeally delay the wakeup and input it in reversed to get it to hit in the right direction, and they are probably going to miss it. And even if they didn't miss it, and got the wakeup to come out in the right direction, your jump is safe and you can block.