That's a total misunderstanding. "The prince that shall come" is NOT "Messiah the Prince", but the Antichrist who will BREAK his false covenant with Israel after 3 1/2 years ("in the midst of the week"). We could go into great detail, but when he demands that the temple sacrifices cease, he does that for just one reason -- to initiate the worship of the image called the Abomination of Desolation. See Revelation 13.
No. You've completely misinterpreted that prophecy. The firm covenant that was established was by the Messiah, in the MIDST of the 7 years, meaning 3 1/2 years after his anointing, which then, by his own sacrifice, he ended offerings and sacrifices. This is NOT a coincide, it is the truth. THEN, after the Messiah did this, after the 70 weeks prophecy, THEN came the prince to come, around 70 AD, the one who would destroy Jerusalem and the temple, which was Titus, who later became emperor, through whom Roman popes would come, who according to the historian Josephus was exalted by his own soldiers at the temple site, which is why Yeshuah said, "when you see the abomination of desolation, then let those who are in Judea flee, because its desolation is near". This is not so difficult to understand, but boy, is it so difficult to those who have been indoctrinated into lies to unlearn their lies! It would be better that they be unbelievers and ignorant, and learn the truth firsthand, than to become a believer and learn lies, because believing the lie makes it all the harder to believe the truth, over someone who is just plain ignorant and will readily believe. This is why the kingdom of God must be received like children, who readily believe what they are told.