Thank you for the translation, as always!
Pretty depressing that even with Eko's sacrifice, Tatsuki was still killed by Hal (when he reverted the ranking battle rules)....
It makes me wonder though if Eko foresaw him dying earlier than that though. Like in the case that Hal succeeded in the Fukurou gamble and gave up his other identities to continue to follow Baku. Hal was afraid then that Baku would kill his dad, so I wonder if Eko prevented a future where that did happen (Baku killing Tatsuki with Hal by his side)?
Other people have already pointed this out, but yea, there are a bunch of examples of blind people who know how to echo-locate. Hal was already shown as someone who could pick up/memorize/learn things really fast (like with the picture book flashback), so it makes sense to me for him picking up echo-location from the video of his mother. Especially since it's like the only thing linking them together, like as if it's her one gift to her son.
Edit: Something I wanted to point out but forgot to, in the Tatsuki image he isn't wearing his earring (he has it when Hal is a little kid though (412)). So I like to imagine he got it after Eko's passing, and wearing it is his way of remembering/mourning her, if that makes sense.