Coffee- The promise was made to bnei Avrohom- not to the unrelated masses who believe in one of his “sons” teachings- which again is saying that H-shem changed his torah and made a mistake the first time around. The promise to Avrohom was still kept to a segment of Klal Yisroel. I believe I heard this from R’ Avigdor Miller ZT”l. He has a fascinating tape on how to answer-it’s quite entertaining.
He also mentioned that the giving of the Torah was witnessed by millions, now how plausible is it that when taking it back and giving it to another it is witnessed by only one person. (and you expect a Jew to believe that-try a better sales pitch) Also, there is no historian of the time of J that ascribes divinity to him. The claim of divinity was made a century later by people who could not have witnessed it, where as the Torah has everything recorded- the Xtians do not deny the veracity of the torah-they only claim it was changed afterward.