Can i keep reloading if i were to lose SA and if so do i add extra time to the timer or does the timer and the end of the mission still count?

If you reset during a full game run, add the time shown on the mission timer HUD, when you reset, to the total in-game time.

The mission timer is shown on Options -> HUD -> Mission Timer from main menu of game.

Loading saves is not allowed, only resetting the mission completely.

K