The spell has no knockback according to my spell editor and spell parser, and it is not doing any pushback in game for me right now in tests, either with the target attacking the pet or a 3rd party. Not sure what to tell you, there; it just doesn't have a knockback.
More is more imo, but how much more would be needed before it counts as "better"? 5% more? 10% more? How much is the water healing effect worth? I wouldn't think very much, it's only like 2% of the water pet's hp (at most) every 15 seconds.