John, it occurred to me that that there is an additional scenario for your question 1.
Resources assigned to Summary tasks.
This is actually one of the reasons why PMs should not assign resources to summary tasks. Anyway, consider the following scenario.
Bob is assigned to Summary Task with 80 hours of remaining work.
Below Summary Task are sub-tasks 1-5.
As time is reported on Tasks 1-5, the total %Complete across Tasks 1-5 is summarized up to the Summary Task. Lets assume that actual work across Tasks 1-5 summarizes so that all 5 tasks in total are 50% complete. When this %Complete value summarizes to the Summary Task, the Summary Task now shows 50% complete (you as the PM did not enter that). Because Summary Task is now 50% complete, Project assumes that Bob’s work assigned directly to the summary task must also be 50% complete and as such, moves 40 hours to Actual Work.
To summarize, if a resource is assigned directly to a summary task, the summarized %Complete for all sub-tasks will roll up to the summary task and project will then adjust the Actual Work/Remaining Work for the resource assigned to the summary task to match the %Complete value rolled up to the summary task.