Let's get some things cleared up.
A goal cannot be awarded, the ball never crossed the line in its entirety. Having said that, the referee could award a goal claiming he 'thought' it did cross the line completely before the medic cleared it.Law 10"A goal is scored when the whole of the ball passes over the goal line, betweenthe goalposts and under the crossbar, provided that no infringement of theLaws of the Game has been committed previously by the team scoring thegoal."
Play should have continued until it was stopped by the referee. whether that was as soon as the medic headed the ball or 10 seconds later, it is when the referee blows his whistle to halt the game.
At this point, a drop ball would be given.
If a drop ball was given, it was not in the box.Law 8"The referee drops the ball at the place where it was located when play wasstopped, unless play was stopped inside the goal area, in which case thereferee drops the ball on the goal area line parallel to the goal line at the pointnearest to where the ball was located when play was stopped."
The guy who attacked the medic should have been sent off or at least cautionedLaw 12"He is also guilty of violent conduct if he uses excessive force or brutality againsta team-mate, spectator, match offi cial or any other person."
In the interest of sportsmanship, the defending team should have probably deliberately conceded a goal after the restart of play. But there is no rule as such and the referee has no power to force them to.