In beginning to answer that question, it should be noted that the phrase "word of God" is only used to refer to Scripture a few times in the Bible. Indeed, of the forty-eight times this exact phrase is used in Scripture (KJV), only four of those are in the Old Testament. Of those forty-four instances that it occurs in the New Testament, only one of them is a direct reference to Scripture (Mark 7:13); and that refers to a specific commandment (Mark 7:10). All of the other instances where this phrase is used are references to the message that God gave to John, Christ and the twelve apostles!
The Gospel According to Luke states that "the word of God came unto John the son of Zacharias in the wilderness." (Luke 3:2) In this same book, we are informed that the people came to Christ "to hear the word of God." (Luke 5:1) In the book of Acts, we are told that the disciples "spake the word of God with boldness." (Acts 4:31) A little later in the same account, we are informed that "the word of God increased" in the hands of the apostles. (Acts 6:7, 12:24) Later still, we are told that Paul and Barnabas "preached the word of God in the synagogues of the Jews" at Salamis. (Acts 13:5) Now the Jews were accustomed to hearing the Scriptures read to them every time they gathered in their synagogues, but notice that this scripture makes plain that Paul's and Barnabas' message was the word of God! Following this, we are told that Sergius Paulus "desired to hear the word of God" from Paul and Barnabas. (Acts 13:7) Finally, we are informed that almost the entire city of Antioch came together one Sabbath "to hear the word of God" from Paul's lips. (Acts 13:44) Likewise, Paul told the saints at Thessalonica that they had received the word of God from him. (II Thessalonians 2:13)
The Gospel According to John goes even further. We read there: "In the beginning was the Word, and Word was with God, and the Word was God...And the Word was made flesh, and dwelt among us, (and we beheld his glory, the glory as of the only begotten of the Father,) full of grace and truth." (John 1:1, 14) Notice that John says that Jesus Christ was/is the personification of the word of God. He is also referred to as the "Word of God" in the book of Revelation. (Revelation 19:13)
In this same vein, Christ claimed that he was "greater" than the temple (Matthew 12:6), Jonah (12:41), Solomon (12:42), Jacob (John 4:12-14) and Abraham (John 8:53-58). In the book of Hebrews, we are told that Christ was superior to Moses. (Hebrews 3:1-6)
Moreover, Christ clearly believed that he had the authority to modify and change the things in Scripture that had been attributed to Moses. Notice how Christ amended many of these teachings with the preface "Ye have heard that it was said by them of old time..." (Matthew 5:21-22, 27-28, 31-32, 33-34, 38-39, 43-44) In fact, his contradiction of Moses' teaching on the subject of divorce is made even more apparent in the account of his confrontation about this by the Pharisees. (Matthew 19:3-9) After stating that God did not intend for His people to divorce, the Pharisees asked him "Why did Moses then command to give a writing of divorcement, and to put her away?" (verse 7) Notice Christ's reply: "Moses because of the hardness of your hearts suffered you to put away your wives: but from the beginning it was not so." (verse 8) In other words, Moses was wrong!
"Isn't Christ affirming the Genesis account of creation here by stating 'that he which made them at the beginning made them male and female'?" Is he? Is Christ talking about the Genesis account of creation or the principles behind God's view on divorce? Isn't he affirming here that God is the Creator, and the One who designed a man and a woman to function as husband and wife? In the final analysis, is Christ really affirming anything about the mechanics of how they were created?
To be sure, Christ and his disciples constantly referred to stories in the Old Testament and quoted those Scriptures in their messages to the people of the First Century; but I don't recall a single instance where they passed judgment on the scientific or historical veracity of the material they were using. "Didn't their use of the material imply that they accepted it as fact?" Did it? Or were they using stories and writings that the people were familiar with to make their own points about what God expected of them and wanted for them? Do you think that all of the men who wrote those prophecies about Christ and his ministry expected them to be interpreted and fulfilled in the manner that Jesus and his disciples used them? In short, was Christ confirming what others had written or was he using their writings to preach a message about salvation through him? Ultimately, I guess we all have to answer these questions to our own satisfaction.