Mrak

For Mrak's rolling card (movement over obstacles), is there a reason for skipping one empty space, or is it just to make the card stronger?

another channel

Mrak's level 3 red card was originally described on Tabletopia as "a another discard", but the physical version has removed the word "another". Does this mean the actual effect has changed? When Mrak is targeted by Whisper's gold card and discards the level 3 red card, can the red card be retrieved? Will the subsequent "This round" effect be affected?

Yes, it can be retrieved. That is what I meant by that yes in my response. As for the no, the tabletopia version of this card and the printed version of this card are identical.

If Mrak has already placed tokens with his gold, can he play silver and place fewer than three tokens, or none (neither of which is "exactly" three)? Do the tokens ever move when spawned?

No. The card specifically says “exactly”. I recommend checking “Place” on page 18 of the rulebook.