I'd agree that your list includes many items that can cause execution to lengthen. But those are all directly related to the execution of the application code itself.
Also consider events which have nothing directly to do with the application itself such as:
Context Switching: IF another process is allowed to preempt your application, there is a cost to saving and restoring your process's state, not to mention the unknown time that the other process will run. Your scheduling algorithm will determine if this is a cost and steps that can be taken to control it.
Device interrupts - usually the process being interrupted is still considered the current process, but system level interrupt handling code is the code running. The current process waits until the interrupt is handled and a Return from Interrupt instruction restores the process state and process instructions resume. Interrupts can occur at "random" intervals and it is difficult to accurately predict the effect on any given run of a process. It's possible to measure average numbers of interrupts and interrupt stack time on some systems and use those averages. Time spent in individual interrupt routines is largely dependent upon the programmers who wrote the routines. Best practice is to do the minimum required processing in the interrupt routine and provide some mechanism for less critical processing to be done later at a lower priority. For VERY critically time sensitive code, interrupts can be blocked on most systems (by privileged code), but again best practice is to limit this code to the minimum.
Interval Clock Interrupts - These are more predictable than device interrupts but also stop the flow of your program to perform system level activities (updating system clocks, check scheduling queues, checking timer events, etc.).
Hardware errors - These are events that are unpredictable and cause interrupts that behave similar to device interrupts. Error interrupts are not always able to be blocked, but if these are occurring it is usually possible to eliminate them by repairing the hardware.