I have no idea why you would cite this map as a proof that Slavs existed in bronze age. Do we have any written document from around 1000 BC stating the location and existence of Slavs? Perhaps it would be different if they've talked about Proto-Slavs or Balto-Slavs, and in very unspecified location.
Furthermore, we have this map, that describes the area of, what they call, Baltic Culture. We have not slightest clue if this culture have anything to do with today's Balts, do we? Are yo sure that this Baltic culture has any continuity with Baltic tribes of iron age?
And yes, the language is a part of a culture. On other hand genetics can't describe Slavs exactly either. It is all in realm of statistics and self designation. I believe we had this conversation some time ago. You want to be a Venet, but are you really? Or maybe you are, because you really want to be?
I don't really care,... lol. But this is life, blurry lines, unspecified borders, incomplete definitions, lots of blending and grey areas. And everything is in flax of constant changes, that blurs things even further.