Yes. Melchizedek is Jesus.
We do not know all truths, only some have been revealed. You make assumptions from the limited truths that we know to state something as factual.
Yes some details in scripture are difficult to understand correctly and require a mature faith to attempt. But, when the details are still unclear, we can't assume a certain truth. Scripture hides things, but God does not deceive us. The words chosen are the best possible words to tell the truths God wants us to know. If Melchizedek was definitely the Son of God/a preincarnate Jesus then scripture should have used clearer words instead of vague ones like in the same order as Christ.
Let me show you another place where a similar thing happened. When Jesus was asked about the prophecy of Elijah returning to earth, Jesus did not refute the truthfulness of this thinking. He actually asserted it and stated that John the Baptist
IS Elijah. Further he added that he would come yet again. Now Christians do not follow to reincarnation, but here we see something like it.
My point is not to debate reincarnation. I wish to point out the specific words used in scripture and note the distinction between the words used by Jesus in Mathew compared with the words used in Hebrews. Jesus did not say John the Baptists is in the same order as Elijah. He did not say he has the same authority or power of Elijah. He said he is Elijah. All the people that argue "This is my body" should not take this distinction lightly.
We don't know how John the Baptist was Elijah just as we don't know how Jesus was in the same order as Melchizedek. But, it is a stretch to claim that Melchizedek was Jesus.
Matthew 11:14 And if you are willing to accept it,
he is the Elijah who was to come.
Matthew 17:11 Jesus replied, “To be sure,
Elijah comes and will restore all things. 12 But I tell you,
Elijah has already come, and they did not recognize him, but have done to him everything they wished. In the same way the Son of Man is going to suffer at their hands.” 13 Then the disciples understood that he was talking to them about John the Baptist.
Heb 7:3 Without father or mother, without genealogy, without beginning of days or end of life,
resembling the Son of God, he remains a priest forever.
11 If perfection could have been attained through the Levitical priesthood—and indeed the law given to the people established that priesthood—why was there still need for another priest to come,
one in the order of Melchizedek, not in the order of Aaron?
17 For it is declared:
“You are a priest forever,
in the order of Melchizedek.