First question...Kearsley Junction/where PM Belt Line intersected with OLD GTW mainline.
Second question, you have it right.
Third question...I don't know if it actually had a name for the crossing in Downtown Flint, but may have been Crapo something because he was the head of the Flint Pere Marquette RR at the time the rails were built thru downtown Flint. (Doug Hefty chime in anytime here for your input)
Fourth question...I've always known it as E. Belsay junction. There also used to be a small yard between Genesee Road and Belsay road to service AC sparkplug, and it was also known as Belsay yard. The title of Kearsley Junction was never a GTW thing, only PM/C&O/Chessie/CSX. Atwood junction is best described as the section of trackage from just south of Atherton Road to just south of Maple road, which does take in the junction you so describe. There used to be an actual wye of sorts within the junction trackage, until GM fisher body closed in 1987. The north end section of the wye came off the mainline just north of Bristol road, switch points facing north, traveled west across Dort Highway thru the concrete place that is still there, and connected to the old mainline just north of Bristol road switch points facing north. From there, to make the complete wye, the old mainline south to the connection with the new bypass line by Maple road, and then back north to the first switch I mentioned here completed the wye. The old mainline stayed quite busy from Grand Traverse Street south to Maple until GM shut the old Fisher Body plant in 1987. Trackage thru downtown Flint was pulled by GTW first, around 1966,and C&O in the 70's, but I don't recall the exact year. Also, PM/C&O/Chessie/CSX had a small yard near Grand Traverse called Deming yard. When I-475 was built around 1980, it went right over the top of the south end of Deming yard. As for your last question, the actual junction of those two points was known as McGrew junction.