Should we translate כָּבֵד as אִתְיַקַּר or יַקִּיר, in Onkelos?

Summary: Some printers follow Rashi's emendation. But did he intend it as an emendation, or was he arguing with Onkelos?

Post: In parashat Vaera, consider the following Onkelos, according to the nusach Teiman:

ז,יד וַיֹּאמֶר ה אֶל-מֹשֶׁה, כָּבֵד לֵב פַּרְעֹה; מֵאֵן, לְשַׁלַּח הָעָם.

וַאֲמַר יְיָ לְמֹשֶׁה, אִתְיַקַּר לִבָּא דְּפַרְעֹה; סָרֵיב, לְשַׁלָּחָא עַמָּא.

This appears to be at odds with Rashi on the pasuk:

14. The Lord said to Moses, "Pharaoh's heart is heavy; he has refused to let the people out.		יד. וַיֹּאמֶר ה אֶל מֹשֶׁה כָּבֵד לֵב פַּרְעֹה מֵאֵן לְשַׁלַּח הָעָם:
is heavy: Heb. כָּבֵד. Its Aramaic translation is יַקִיר [heavy], and not אִתְיַקַר [has become heavy], because it is the name of a thing [an adjective and not a verb], as in for the matter is too heavy (כָבֵד) for you (Exod. 18:18).		כבד: תרגומו יקיר, ולא אתיקר, מפני שהוא שם דבר, כמו (שמות יח יח) כי כבד ממך הדבר:

The reference is to a pasuk (and Onkelos) in parashat Yitro:

יח,יח נָבֹל תִּבֹּל--גַּם-אַתָּה, גַּם-הָעָם הַזֶּה אֲשֶׁר עִמָּךְ:  כִּי-כָבֵד מִמְּךָ הַדָּבָר, לֹא-תוּכַל עֲשֹׂהוּ לְבַדֶּךָ.

מִלְאָה תִּלְאֵי--אַף אַתְּ, אַף עַמָּא הָדֵין דְּעִמָּךְ:  אֲרֵי יַקִּיר מִנָּךְ פִּתְגָמָא, לָא תִּכּוֹל לְמִעְבְּדֵיהּ בִּלְחוֹדָךְ.

It is unclear if Rashi is (a) emending the text of Onkelos in Vaeira, (b) arguing with it, or (c) selecting from variants texts which stood before him.

In the beautiful Tafsir PDF, in Chelek Hadikduk, we have the following analysis:

"The Targum in old nuschaos is אִתְיַקַּר, and in printed editions, there are some that are gores אִתְיַקַּר and some that are gores יַקִיר. And certainly they emended it to be such based on Rashi.


And in truth, Rashi's intention was not to Targum Onkelos, but rather his intent was that its explanation was so. And in fact, he intended to argue with Targum Onkelos.


And see in the Re'em (Rabbi Eliyahu Mizrachi) that even though כבד is a שם {an adjective}, we make from it a past tense verb, just like zakein, which is a שם and despite that we make from it an action, such as in כי זקן יצחק."

See also Shadal, in Ohev Ger, on this.

"כָּבֵד לֵב פַּרְעֹה -- is אִתְיַקַּר לִבָּא דְּפַרְעֹה (in מא"ר, יא"ר, לסבונה and רע"ח, =, Savyonita, Anvirsa, Gimel Targumim, and ח"ג). And Rashi emends to יַקִיר, and after him followed a few of the printers. 


But it is an error, that which is written in Nesivos Hashalom {from Mendelsohnn): In old Nuschaos of Targum Onkelos it is יַקִיר, and in new ones אִתְיַקַּר.


And in my opinion, כָּבֵד is in past tense, by the evidence of the word מֵאֵן which follows after it, which is past tense, and had it stated ממאן, it would have been possible to say that כָּבֵד is an adjective. [קע"א has אִתְיַקַּף]"