Unless my memory is failing me, the observers who wrote "Darwin's Finches" made quite an extensive study of all the breeding going on in the Galapagos, including of crossbreeds, and their conclusions were not that the crossbreeds were more highly successful than the purebreeds, contrary to what you've suggested.
The so called 'scientist' who originally made the claim that these finches proved evolution was made by Percy Lowe in 1936. Evolutionists blindly followed him without bothering to verify the claims because of course it backed up their theory. The refutation came from Peter Grant and his colleagues who observed in 1982 that the various finch breeds produced hybrids. This throws down all the nonsense mentioned by evolutionists about the finches and shows quite well the dishonesty of evolutionists who continue to use this as an example of evolution even after it has been comletely disproven.
So all that effort I put into explaining to you that speciation isn't a cut-and-dried separation event was for nought? The finch example is still fine evidence, speciation does not have to be total for the finches to be provide a good example of it, any more than donkey and horse, or camel and llama, or herring gull speciation needs to be total.