I want my resources to be notifed of their assignments.

This setting can be handled in my preferences in 8.4. A setting in my preferences allows you to enable them to be notified when they are assigned or removed from an activity. You can also be prompted before the email is sent.

Can you update physical and duration % complete at once?

Yes, you can do so, but it may be easier to grasp by doing so in the column view of the activity.

How to update project progress in the P6 web

To determine how a project is performing and what remains to be done, update its progress. Updating a project to reflect the actual work performed to date can be achieved using any of the following methods:

Manually record progress: Record progress for individual activities or resources by entering status data from each member of the team.

Automatically calculate progress: For individual activities, resources, and expenses, use the convenient Auto-Compute Actuals feature to estimate work progress based on the schedule plan. Then, run the Apply Actuals feature. Using these features, the application calculates and applies the expected progress from the previous data date to the new data date you specify. To regularly update a project so that it reflects current actual and remaining values, run the Apply Actuals process using the Scheduled Services page.