Do you know Biblical Hebrew? If you are merely quoting the English translation, I'm afraid you will need to do better than that. Those whom I know that do know Biblical Hebrew have assured me that it is past tense in grammar, as the translation I posted showed. Also, it is saying that HaShem shall call this person the "prince of peace", listing multiple titles for HaShem. I have also been assured this is a proper rending of the Hebrew.
Here is from a Jewish-English translation:
Isaiah 9
Complete Jewish Bible (CJB)
For a child is born to us,
a son is given to us;
dominion will rest on his shoulders,
and he will be given the name
Pele-Yoetz El Gibbor
Avi-Ad Sar-Shalom
[Wonder of a Counselor, Mighty God,
Father of Eternity, Prince of Peace],
6 in order to extend the dominion
and perpetuate the peace
of the throne and kingdom of David,
to secure it and sustain it
through justice and righteousness
henceforth and forever.
The zeal of Adonai-Tzvaot
will accomplish this.
If this refers to that king, it does not square with what actually happened:
2 Kings 20
16 And Isaiah said unto Hezekiah, Hear the word of the Lord.
17 Behold, the days come, that all that is in thine house, and that which thy fathers have laid up in store unto this day, shall be carried into Babylon: nothing shall be left, saith the Lord.
18 And of thy sons that shall issue from thee, which thou shalt beget, shall they take away; and they shall be eunuchs in the palace of the king of Babylon.
19 Then said Hezekiah unto Isaiah, Good is the word of the Lord which thou hast spoken. And he said, Is it not good, if peace and truth be in my days?
20 And the rest of the acts of Hezekiah, and all his might, and how he made a pool, and a conduit, and brought water into the city, are they not written in the book of the chronicles of the kings of Judah?
21 And Hezekiah slept with his fathers: and Manasseh his son reigned in his stead.
For one called "The Mighty God," it does not sound like he had walked as well as David. In that time, Israel also suffered many horrors. The Kingdom did not extend. It diminished, and his life was ended with the dread prophecy of exile into Babylon. He also was not a child when that scripture was written, and the promises of everlasting peace are things strictly limited to the Messiah Himself, not to this King.
Eze 37:21-25 And say unto them, Thus saith the Lord GOD; Behold, I will take the children of Israel from among the heathen, whither they be gone, and will gather them on every side, and bring them into their own land: (22) And I will make them one nation in the land upon the mountains of Israel; and one king shall be king to them all: and they shall be no more two nations, neither shall they be divided into two kingdoms any more at all: (23) Neither shall they defile themselves any more with their idols, nor with their detestable things, nor with any of their transgressions: but I will save them out of all their dwellingplaces, wherein they have sinned, and will cleanse them: so shall they be my people, and I will be their God. (24) And David my servant shall be king over them; and they all shall have one shepherd: they shall also walk in my judgments, and observe my statutes, and do them. (25) And they shall dwell in the land that I have given unto Jacob my servant, wherein your fathers have dwelt; and they shall dwell therein, even they, and their children, and their children's children for ever: and my servant David shall be their prince for ever.