1. Dead reckoning. Height against distance to STAR altitude. Regular checks because of wind speed differences with altitude. Also makes sure you can get the Cabin Pressure down within descent limits.
2. Deceleration times with regard to pattern limiting speeds. Regular checks of distance to runway threshold.
3. All the time. Use A/P to help, not to dictate your actions.
4. DON'T USE THEM unless ATC cause a change in your profile and you need a rapid adjustment. Costs fuel.
5. Few. You should anticipate changes using overall height/ distance to runway threshold, by being familiar with the requirements of destination ATC.
6. Once or twice, when given late descent because of traffic ahead. You won't get into this situation if you think "outside the box". Maybe slow down earlier ?
7. No. I would probably go manual and adjust power to suit, following the Flight Director, but this is probably against today's philosophy !