The passive math is fine...
Getting skaarl back restores up to 80% of Skaarl's HP, which is equal to Skaarl's base hp plus your bonus HP.
One of his Q's DOES knock you back.
The shortening tether gets short enough by the end of the duration that Kled pretty much never pulls in someone he doesn't want to pull in. The slow is mediocre as a defensive tool, but it is there.
The second dash is rarely used defensively. That said, you can use it like that if there is a monster in your escape path to dash through.
Your ult is very wide, but Skaarl won't turn around to tackle a target that is behind the duo unless they are pretty much on top of you (like a Sion ult). That semicircle range indicator you see while ulting is the area in which Skaarl will give the first enemy a flying hug.