So this is alot...lets tackle this one at a time eh?
I think its important to lay the basis that for Fresh to work in MCQ I had to get rid of the 'parasite' aspect because the story I wanted to tell fell apart if we went that route, so I made up for that loss of the canon with the introduction of his dimensional powers, and those powers are what give him the ability to be aware of other dimensions. This, in universe, however is an exceptional ability.
ZigZag was originally designs as a fresh parasite yes, but thats why I like the joke so much. :) Because at the time I was still even getting self ship fanart with Fresh, and because I designed ZigZag, the joke was 'its like you and Fresh had a kid!' and I ran with it. XD I've always been self insert trash anyway and I see no reason to stop that now.
As for how good at parenting Zig's parents are you're just gonna have to wait and see! I'll be more willing to answered detailed questions once I'm certain what scenarios we'll be seeing in comic.
If you're referring to the comic I did where Fresh and True!Fresh had an interaction, yes you can consider that interaction canon but no, it is probably a one time event. I can't see True!Fresh bothering Worldview too much - there's far too much surveillance there.