I'm on the steam XCE branch and I can confirm these bugs. Game crashes when AI gets reaction fire. Game crashes when I target explosives (stun grenades, rockets, regular grenades) in a manner where an alien would be in the AoE. When an alien kills a xenonaut, the game doesn't crash, but hangs perpetually and the AI turn never ends.
removing "<DeadSoldierNotificationDuration>3.0</DeadSoldierNotificationDuration>" from config.xml in the CE settings mod seems to have fixed the AI hang. but not the others.