If you find a well maintained one there's nothing wrong with Vitz. CVT issues are repairable here for some extent. I have used a 2007 one for 4 years as 3rd owner only dong regular services and climbed mountains with it. It really depends on how it was maintained by previous owner/s. Car has nothing to do with Sri Lankan second hand logic what so ever.
You can fill all those marks up with paint, but it will still be visible upon close inspection because they're deep and have penetrated primer layer into the plastic.
For a neater job, you'd have to sand those burs down, use a bit of glazing putty, wet sand it and then paint over it.
Also, get your dog a (less expensive) toy to keep munching.