Awaken targeting rules
You've mostly answered the question yourself, including the ruling quotations. Yes, paying Awaken cost will add a new target (a land), so if you make a first target illegal, it won't counter the spell to the full extent. And vise versa, as even mentioned in the linked article:


  Also, if a spell with awaken normally doesn't require a target, and you choose to cast it for its awaken cost, you will add a target to the spell by doing so. If that target land becomes illegal before the spell tries to resolve, the spell will be countered. You won't get any of its effects, including the first effect that didn't require a target. This won't come up a lot, but it's definitely something to be aware of.