Why is "och" (and) not spelled "og" in Swedish?

Question

For example, here is the word for "I" in the Old Norse dialects.

• Old East Norse = Jak
• Old West Norse = Ek

These words became, with a natural evolution, the following:

• Icelandic = Ég
• Faroese = Eg
• Bokmål = Jeg
• Nynorsk = Eg
• Danish = Jeg
• Swedish = Jag
• Elfdalian = Ig

Here is the word for "and" in Old Norse (both dialects):

• Old Norse = Ok

And again, the same changes occured, except for Swedish:

• Icelandic = Og
• Faroese = Og
• Bokmål = Og
• Nynorsk = Og
• Danish = Og
• Elfdalian = Og
• Swedish = Och (pronounced like a k)

Why didn't this change occur in Swedish?

The same thing applies for others words like "you" ("þik" became "deg", "þig", "teg" and "dig").

Answer 1

In the earliest Swedish written using the Latin alphabet, such as the Äldre Västgötalagen from about 1250, the word is spelt 'ok'. It seems to have changed to 'och' during the later middle ages or early modern period, when 'decorative spelling' (dekorativ stavning) became popular. One possibility is that the modern spelling is therefore a relic of decorative spelling.

However, in contradiction to that, the Swedish Etymological Dictionary states that "Stavningen och bevarar minnet av ett forntida uttal med ach-ljud" ("the spelling och preserves the memory of an ancient pronunciation using the ach sound" [that is, a velar or uvular fricative]).

Answer 2

When unstressed, Swedish "och" is phonetically [ɔ], which isn't any different from Norwegian "og" [ɔ]. Referencing Danish is really not that informative as Danish has voiced most of its consonants so that even if it had "*ok", it would've gone to "og" either way (a generic example: Danish vs. Swedish bog & bok 'book'). My thoughts on it are that stressed "och" preserved the hard plosive while its unstressed variant lenited it to [ɣ] which was lost almost everywhere. Irregular sound changes, sure, but those are abundant and particularly full of holes.