Your feeling no different to what i felt. Met and Gen Nav absolutely killed me when i was doing them, but they ended up my best marks !!
You are doing the right study methods and very similar to myself.
Make yourself a study timetable and planner, so you know what you have to do and stick to it. There will be times when you will think 'Forget it...I can't be bothered'....stick with it.
I do the same as you. I create bullet points for each chapter on the PC generally covering essential facts and figures, and completing the progress tests as i go along.
Once i have finished all the modules, i then go back to the start and just read each chapter start to finish, doing the progress tests again. You will be surprised at how much you have retained!! Once at the end of that i then read the bullet points i have made, and again completing the progress tests again. To learn this much information you can only do it by repitition.
By this time you will have a good idea on what are your weak areas/subjects and what you have mastered.
Now plan a revision timetable. Allocate more time to the harder ones and less to the easier subjects. Start reading again. Make sure you understand aspects. Look at alternative ways of working problems that work for you. For Gen Nav concentrate on getting quetions answered in a time limit. That is the real enemy in that exam. You simply run short of time. If your really stuck ring or e-mail Alex and get some extra guidance.
Be about 90% prepared to sit your exams when you go to BGS. The first week is mainly concerned with going over the syllabus with feedback papers thrown in. The second week is mock exam, after mock exam, and this gets you into the correct methods of reading and being able to answer the questions.
You cant remember everything, but get the basics mastered and the rest just seems to join on the more you read.
Best of luck !!