The various figures you mention assume there is no argument about their accuracy, nor for that matter the figures I mntioned. So perhaps the boloid events are closer to some other measured events.
You mention that glaciation in Antarctica started about 42 mya. Other comments refer to later figures, although those could refer to well developed glaciation, not the beginning. Interesting factoid: If you look at the sea mounts leading off from the Hawaii hot spot, you will see that at first they trend east north east, then there is a sharp movement more directly to the north. I believe the age given for this directional change was around 43 mya. So the question, if my memory and their figures are correct, did some major event start the Antarctic glaciacion?
I really hope that more interdisciplinary work will be done on identifying and dating all these different major events—boloid, volcanic, seismic, etc. Only then will it be possible to develop the most accurate theories and come to conclusions that most people will accept.
I think what really happened with the Antarctic glaciation timeline is that:
1) Antarctica was already more-or-less over the South Pole as early as 60 million years ago and a few glaciers developed on the higher mountain ranges particularly about 42 million years ago; but,
2) It was also connected to South America and Australia at the time so that the ocean currents were mixed with mid-latitude/tropical ocean currents in gyres in the Pacific and the Atlantic/Indian Oceans which keep it reasonably warm - still frigid in the Winter but the snow and ice melted in the Summer.
3) About 34 million years ago, enough separation occured between South America and Australia, that the Antarctic Circumpolar Current developed which isolated Antarctica in an extreme polar climate.
4) It rapidly glaciated over after this.
5) About 27 million years ago, some jostling of the small cratons between South America and Antarctica closed off the Antarctic Circumpolar Current again and the glaciers melted back considerably.
6) About 14 million years ago, the Circumpolar Current was re-established and Antarctica glaciated over again.
7) About 2.5 million years ago, the Earth cooled off even more (due to events in the Arctic ocean which are still not explained other than Greenland and the Arctic Archipelago were slowly drifting north), and Antarctica glaciated over even more than previously more-or-less similar to today.
That is my timeline of events and I have spent a lot of time researching this. I could quote about 50 sources but I hate doing that.
Antarctica was also glaciated over between 330 to 290 million years ago, 430 to 420 million years ago and 640 to 600 million years ago when Continental Drift also placed it near the South Pole. It is the unlucky Continent.