Messiah: Stripe or Stripes?

I was recently helping a friend of mine translate Isaiah 53:5, and came across the phrase וּבַחֲבֻרָתוֹ נִרְפָּא־לָנוּ "and by his stripe we are healed." He mentioned that another friend of his had made a significant theological point on the MT reading of חֲבֻרָתוֹ "his stripe" being singular. I pointed out, however, that the consonants could also be easily emended to the plural חֲבֻרֹתָיו "his stripes."

Though in most cases (as far as I can tell, all cases) the plural would have an extra י as in חברתיו, the two forms could easily have interchanged in the tradition. Ironically, in my reading in Ezekiel immediately thereafter, exactly such an interchange presented itself repeatedly. In Ezekiel 43:11, MT twice reads the singular phrase צורתו "its plan" as the Kethiv and the plural צורתיו "its plans" as the Qere. Furthermore, in both Ezekiel 43:11 and 44:5 MT has תורתו "its law" as the Kethiv and תורתיו "its laws" as the Qere. The same phenomenon can be found in Exod 28:28; 37:8; 39:4; Deut 5:10; 7:9; 8:2; 27:10; Josh 16:3; Ruth 3:14; 1 Sam 10:21; 26:7, 11, 16; 2 Sam 12:20; 1 Kings 16:19; Ezek 31:5; 33:13, 16; 40:6, 22, 26; 47:11; Amos 9:6. It is interesting that only once that I found, in 1 Kings 16:26, is the situation reversed with the plural in the Kethiv and singular in the Qere, showing a definite trend towards the plural in the Qere. This may show an understanding that haplography in such examples was more common than dittography. Perhaps noteworthy, however, is that this phenomenon apparently never occurs in the book of Isaiah.

After examining these other occurrences of the interchange between the תו and תיו endings, I was even more suspicious of the theological point based off of the singular חֲבֻרָתוֹ in Isaiah 53:5. Brief consideration of the LXX showed the singular reading τῷ μώλωπι αὐτοῦ "by his bruise," which slightly alleviated my fears. I decided to check the Great Isaiah Scroll 1QIsa(a) for curiosity's sake, and much to my surprise, it reads the plural חבורתיו! My suspicions (viz., my diagnostic conjectural emendation) were correct! The plural was indeed an ancient Hebrew variant that did not make its way into the Masorah of MT. 1QIsa(b), normally much closer to MT, had the singular חברתו.
All this to say, the singular "stripe" in Isa 53:5 may not be as significant as we make it out to be, or it may not even have been original. Perhaps we were healed by Messiah's "stripes" after all? One would be hard pressed to overthrow the singular reading with the single Qumran scroll, but I think this example proves that my cautious skepticism about basing significant theological points on textually dubitable minutiae is indeed warranted. It is the nature of language and exegesis that often important information must be drawn from the most precise of details, but this just goes to show that the exegete cannot naively assume the Leningrad Codex as his text without critically evaluating its readings for the given passage. Criticism of the text must precede exegesis of its theology, and any given theological induction from a text is at least as dubitable as its text.