Can anyone tell me how can I tell if I've been effected by this bittrex leak?
Unfortunately, you can't tell it before it happens. There will be some speculations but nothing will be concrete. And if it really occurs, we still don't know if all the users documents will be leaked as its also possible that a portion of it might be not.
It's my first time seeing the site so I don't know it's credibility but by just reading the article, Their evidence is very circumstantial I don't even know if it can really be considered as an evidence as you can't confirm it and view it. And as far as I know bittrex connection is secured, you can check it by clicking the padlock symbol.
But its indeed a problem on why bitrex didn't give any explanation on how they will store the users documents so I guess we can just hold to the fact that they won't mess it up as it's basically a self destruction to them.
Reporting my passport as stolen
Registering for a credit freeze
Change everything associated to bittrex email address
Change phone number
Yes. This should be fine