Mawdsley's quote in that second part pretty much lines up with what Megargee says (Bock is basically saying "both trying to withdraw and holding fast are risky so the Fuhrer has to decide") so I'm not sure how it disagree with his interpretation.
He's saying that both trying to hold and withdrawal come with risk. But he then goes on to outline the disadvantages which withdrawal has that holding doesn't, which does seem to imply that he's for holding, particularly when the other quotes hasdrubal barca provided are taken into consideration.
The first bit, which talks about the 13th, lies outside of Megargee's timespan so I'll have to look into it elsewhere. And your last bit... contains no real information other then Kershaw's opinion.
The chronology would seem to fit with Kershaw's opinion though. Bock gave his assessment on the 13th, but only got it through to Hitler on the 16th. That very night, Hitler made the decision to stand fast. And unless Bock was outright lying in his war diary, Hitler's decision would seem to have been based on Bock's assessment as both Kershaw and Fritz indicate. From the quote of the diary provided by hasdrubal barca, "The Fuhrer then explained, quoting my reasons word for word, the pros and cons of staying or retreating, and came to the conclusion that under the prevailing conditions it made no sense to withdraw to an unprepared position leaving behind artillery and equipment. In several days we would be facing the same situation again but now without heavy weapons and without artillery. There was only one decision and that was not t take a single step back."
It does occur to me, though, that Bock advocating standing fast on the 13th, withdrawing on the 15th, and then just metaphorically threw up his hands and went "I don't fucking know!" on the 16th is pretty indicative of some serious indecision on his part. It is rather understandable given the overwhelming strain from the crisis and his age... but it makes me skeptical of precisely how serious of an impact his advice had on those above him. I mean, if you got a piece of advice from someone one day and then the opposite piece of advice from the very same person the next day... what would you think of them?
Are you sure Megargee places Bock coming up with the the ninety mile retreat idea on the 15th? Because every other source I can find which mentions it indicates that it was brought up earlier, in response to a conversation with Halder. From Samuel Mitcham, The Rise of the Wehrmacht, page 498 "On the morning of December 9, he telephoned Halder... After this conversation... He instructed his subordinate commands to prepare to retreat 60 to 90 miles..." From
this Army Historical Study, "On the morning of the 9th, resuming a telephone conference begun the night before... From there on the exchange trailed off into futility. Bock responded, "By then the army group will be kaputt [smashed]." Halder replied, "The German soldier does not go kaputt!"... After that Bock instructed the army commands to plan to take the entire army group back sixty to ninety miles to the Rzhev-Gzhatsk-Orel-Kursk line. But he did not believe that would help either because it would take weeks to prepare the new line and to start back before then would be "an excursion into nowhere." Furthermore, the equipment losses sustained in the small withdrawals undertaken so far would be multiplied by the hundreds. At best, the potential relief would probably be negligible." So basically it seems the retreat was an idea he never really believed in that he came up with as an emotional reaction to the conversation with Halder which went badly.
In any case, it seems to me that at the very least there was enough support for holding that Goring might very well have decided in favor of it.