Atlantis, the existence is about 11,600 years ago (according to Plato). From this age until today, human has been travelling all over the world bringing his culture, myth, legend, language, religion, etc. We cannot compare the modern civilization to the Atlantis' in respect to the location, language, tradition etc since their origins beyond 10,000 years ago are difficult to trace. My book does not discuss these things, conjectures can be made but with uncertain basis.
Sundaland sank gradually, this is no doubt. The destruction of Atlantis was by a flood (according to Plato). This can be interpreted as a real flood from a river, a tsunami or likewise, this was also possible in the area in question. The observation of the remains of Atlantis was (or were) made some thousand years after its destruction (as written by Plato). The remains were only a few meters below the water. Due to estuary sedimentation, volcanic ash, etc, the location was muddy. It was impassable. If you read my book, the present location in question is also impassable because of the existence of a coral reef.
Talking about domestication origins can be a long debate, even among the experts. The proofs are not easily found and change over time as new evidences found. Proofs in Sundaland are difficult to investigate as it is now underwater. Even, the inland proofs are not easily investigated because they were underground due to volcanic ash as thick as 10 m or more, also under sea water. The existing archaeological remains were mostly found by chance.
Talking about domestication of horse, it is also not so many proof. The oldest evidence that is known is about 5,000 years ago or more in Botai culture, residents of Central Asia. However, Equus ferus, the wild horse as the ancestor of the domesticated horse, inhabited Yukon and Alaska in the Ice Age, which extinct more than 10,000 years ago. The Ice Age horse crossed the Bering Land Bridge into Asia and then Europe. Judging from Siberian Pleistocene mummies, Eqquus ferus looked similar to the wild Asiatic horse. So, it is possible that the horse was also domesticated in Asia, especially Sundaland along with the beginning of civilization in this area.
Anyway, please read my book so that you will see Indonesian Poseidon, physical proofs, name translation, etc, then give me further inputs or comments. By the way, thanks for the above comments.