OOOHHH....the hard questions.
First--in courses with scorm modules, do you see grades in the grade book for the scorms? If you scorms don't report an actual grade (other than 0...), it won't do you much good.
Second--mdl_grade_grades will store your scores if there are scores to be stored---but connecting grade_grades to specific item in a query is a little more complex. Because that table gathers data from all the activity tables, you have to know the item number and id, the user id etc--so the grade_grades table isn't sorted by course as much as...well, item id's which are actually a little less obvious than you might think. If you can figure out which ones you want, you'll want the final grade field. But what you probably want is to connect through the tables to connect the item name and number and grade...which would be a lot of work. I've done something like it using Crystal Reports and it is pretty horrible.
Scorm grades are actually stored in mdl_scorm_scoes_track. But it also stores other tracking data (completed, suspend data, etc), so you would be looking for the element cmi.score.raw (or maybe cmi.score.scaled).
The problem with querying this sort of thing is setting up the table connections and being right about what connects where and what you actually want pulled out.