So...the gradebook is a course only thing...that said, you can probably do what you want...version may be relevant but I'm still on 2.8, so not sure.
I also track training by hours and use a custom field in my courses (I think there is a patch or something...not a tech, not sure it works past 2.9?) that I just provide all the possible credit (and can add more) and the instructor selects from a drop down.
For the reporting you are looking for, I use a plugin called Configurable Reports. It does require SQL knowledge for what you're asking...I have a report that each user can run, see only their credit, course name, activities complete vs required (for some reason it doesn't consider the questionnaire activity an activity for this purpose), course complete/incomplete, date of completion/credit award, hours earned. Mine sorts alphabetical by course title, would be easy to add the category the course is in and have it sort by category. Totals are probably harder (I'm not a wiz at SQL) but probably possible.
Mine doesn't do totals, even for the whole thing, because some of my users are enrolled in courses more than one way (they are in a cohort but self-enrolled before the cohort was enrolled, etc) and the report considers that two enrollments and doubles credit...I'm sure there is a way to fix it but (not a SQL wiz) haven't figured out how (yet). That said, someone with skills could probably do it.
I also use menus for navigation and there is one that provides access to run the 'transcript'. Or...it could be a block or something.