Honesty if you have issues with the historicity or accuracy of the New Testament why add to it by looking forward to Islam rather than back towards Judaism and the Torah??  For me there are 3 issues that keep me from doing so: 1) the fact that the Quran’s accounts of things sometimes differ in critical details from the Old Testament 2) the Islamic understanding of Jesus as “messiah” is so empty it almost seems like Islam has only used it because to do otherwise would have been seen as unacceptable to potential Christian converts in the area as denying that Jesus is the Messiah is the definition of anti-Christ in the Epistles 3) it doesn’t seem like too much of a stretch to think that Islam was GREATLY influenced by heretical Christians in the Arabic peninsula who denied the divinity of Christ.