The translation of the Hebrew word b'rith all depends on the context. In a "religious" context, it would be "covenant"; in a political context "treaty"; in a business context "contract". The authoritative Brown-Driver-Briggs Hebrew lexicon (BDB) has an excellent in-depth discussion of this.
You are absolutely right about the meaning of the word "confirm". In modern usage, it simply means "to affirm or reaffirm that something is true or valid". For this reason, I feel that it should be avoided here, since it "waters down" considerably the meaning for modern readers. The word "enforce" captures the meaning of the Hebrew here exactly.
One can't really define this word one way or another without being given over to one perspective or another concerning who the 'he' is or what is meant by the covenant or treaty. Being predisposed to the meaning of the covenant can changes ones perspective of this word. But even using the word "enforce" to define it, I can apply that idea to how Christs atonement on the Christ fully "EN-FORCED" the power of the eternal Covenant.
Thank you for the three references on Hebrew parallelism; they are all excellent.

However, if there is parallelism here, it can work both ways; it could equally well be an
antithetic parallelism showing parallels between the subjects of verses 26 and 27, for example, Christ versus Antichrist (See your references). It all depends on the identity of the "he" in verse 27.
Since the last part (section 3 below) uses the same words such as desolation or desolate, it seems more likely to me that it would be a synonomous parallelism which would make the 'he' in vs 27 the same as the Messiah.
Logically it should be "the prince who is to come" nagid habba, since (1) it would have been pointless to mention him here unless Daniel (or rather the angel) was not going to say anything about him here and (2) he comes chronologically after the destruction of the temple in 70 AD (v. 26).
Again the chronological reading is empty and unbased if this is parallel literature. And since it is in Daniel and a prophecy, one way the Spirit used to hid the meaning of prophecy was to hide it in the poetry of literature.
Consider this below;
Part 1 talks of the Messiah,
Part 2 talks of Titus, Vespacians son,
and Part 3 talks of the war and desolation of Jerusalem, and judea.
26"And after the sixty-two weeks;
Part A.
1.Messiah shall be cut off, but not for Himself;
2.And the people of the prince who is to come
Shall destroy the city and the sanctuary.
The end of it shall be with a flood,
3.And till the end of the war desolations are determined.
27
Part B.
1. Then (after the 62 weeks, actually 69 weeks) he shall confirm a covenant (new covenant) with many for one week (IN JERUSALEM; vs 24); But in the middle of the week He shall bring an end to sacrifice and offering (he shall be cut off).
2. And on the wing of abominations shall be one who makes desolate,
3. Even until the consummation, which is determined,
Is poured out on the desolate."
Also, the sacrifice and offering were not stopped after Messiah was cut off, but continued for nearly forty years.
Remember your causative verbs?
It says; The destruction of the temple and the desolation was
on the wing of abominations. I can read this as saying that the destruction was caused by the continued sacrifices. AS they were now an abomination to God being types pointing towards the reality of Christ.
The writer to the Hebrews still uses the present tense in referring to the sacrifices (Heb. 10:11). Only the validity of the sacrifices came to an end then.
Yes, and in reading Heb 10, I get the picture that these continued sacrifices were sins which the writer cautions against falling back into.
Heb 10; Now where remission of these [is, there is] no more offering for sin.
For if we sin wilfully (those in 60 AD who become rejudaized and choose again to offer old covenant sacrifice) after that we have received the knowledge of the truth, there remaineth no more sacrifice for sins, (it is already ineffectual)
Of how much sorer punishment, suppose ye, shall he be thought worthy, who hath trodden under foot the Son of God, (by re-offering sacrifice of animal to God for sins) and hath counted the blood of the covenant, wherewith he was sanctified, an unholy thing, and hath done despite unto the Spirit of grace?
But call to remembrance the former days, in which, after ye were illuminated, ye endured a great fight of afflictions;
Cast not away therefore your confidence, which hath great recompence of reward.
For yet a little while, (in 60 AD) and he that shall come will come, and will not tarry.(is this not referring to Titus as the Prince to come in Dan 9;26 and 27??)
But we are not of them who draw back unto perdition; but of them that believe to the saving of the soul.
Now, because of the fullfilled the eternal Covenant of the just dying for the unjust, continued sacrifice is an abomination against God and animal.
2 Cor 3 talks of this;
3:14, And not as Moses, [which] put a vail over his face, that the children of Israel could not stedfastly look to
the end of that
which IS abolished: (even before the desolation, the old covenant was said to be abolished)
Dan 8:19;And he said, Behold, I will make thee know what shall be in the
last end of the indignation: for at the time appointed
the end [shall be].
This verse of Dan 8:19, plus the record of Daniels 4th beast of Dan 7 being the Roman kingdom, plus Jesus' confirming the opening of the seals of Daniels visons which talk of the abomination of Daniel to the people
of that generation; all these give the understanding that Daniels visions refer to the end of the old covenant, and the establishment and confirming of the Eternal "New" Covenant.
I think the 'indignation' refers to the old covenant and it's animal sacrificial system as well as the 'indignation' that individuals of other nations would have felt during the old covenant system.
I am not solidified on these perspectives. However, the individual bible interpreter
MUST ask and answer the question, What does the
'end of the indignation" refer to. It is not saying "end times' and in fact none of the times that the phrase 'time of the end" is used in Daniel seem to refer to "end of the earth", but rather says things like; the end (of the vision) shall its understanding be.
Jesus said to his disciples concerning the establishment of his kingdom.....For it is not for you to
know (ginosko) the times and the seasons.... and none of the disciples except John were alive at the destruction of Jerusalem and the freeing of the Jewish Christians living there.
The transition between the old and new covenants occured and was confirmed
in the times and the seasons that were established by the old covenant from when Moses led them out of Egypt. (Jeremiah 31:31) The transition period to continue to confirm the new covenant were between the Crucifiction and the desolation of Jerusalem and cooresponds to the transition period between the Passover and the crossing of the Jordan. The church of believers were solidified and established free of Judaic oppression in Pella; east of the Jordan where the other nations were first called 'not a people' when Moses said that the Jewish group was now a people of God.
Deut 27:9; And Moses and the priests the Levites spake unto all Israel, saying, Take heed, and hearken, O Israel; this day thou art become the people of the LORD thy God.
Back to 2 Cor 3.
But their minds were blinded: for until this day remaineth the same vail untaken away in the reading of the old testament; which [vail] is done away in Christ.
But even unto this day, when Moses is read, the vail is upon their heart.
Nevertheless when it (the yet elected jewish heart of 60 AD) shall turn to the Lord, the vail shall be taken away.
Consider Rom 11, where the remaining elect of the then blinded jews would be made jealous by the filling of the nations is coming in, beginning with Cornelius.