In 1874, French Orientalist Francois Lenormant analyzed Turkic-Sumerian mythology by comparing Sumerian myths with Central Asian magic and cultural similarities, in addition to comparing Sumerian language with Ural-Altaic languages. He published his book La magie chez les chaldeens et les origines accadiennesconcluding Sumerian to be Turanian.
The last book you quote has, in its description in the amazon link you gave the quote: "How were the ancient civilizations of Sumer and Maya, physically a world apart, actually connected?" That's enough for me to know that I can immediately discount it as fantasy. It falls in the same category as pyramids being build by ancient astronauts.
As for your other sources, I'm glad that 3 people in 115 years found links between Summerian and Turkic. To my limited knowledge, the vast bulk of the experts in this field consider Summerian to be a language isolate. It's wikipedia page doesn't even mention Turkic, and it does mention a lot of other potential family groupings and why they don't have any evidence. This isn't something I care anywhere near enough about to conduct extensive research myself, so I'll trust with the bulk expert opinion unless some exceptionally strong evidence appears to change my mind.