You can photoread as many books as you want in a day. In fact it's often advised to photoread 3 to 10 books a day and activate at least one of those books per week.
You can safely photoread more than one book and on more than one subject. You'll probably find it easier to group them into common subjects.
Photoreading and allowing the class to be the activation session works just fine. You can activate more after the class if you desire. The only time I would suggest you really make the effort to start activating before the class is when the lecturers require you to have 'read the material' before the lecture.
So your idea of mind mapping and activation during class is valid.
Maths material... photoread it anyway. You will still need to do the activation which is doing the working out of the problems. When you get stuck. Try taking a deep breath, photoread the textbook again (from cover to cover) take a 20 minute break and try again. Photoreading works well for all subjects. It's the conscious mind that stalls on taking up the information from either the inner mind or the book. Be patient by photoreading again you're telling your inner mind...'look at this again and present it so that my conscious mind understands'.
Yes photoreading the material daily is Okay and can be a good Idea. Not absolutely necessary, so if for some reason you cannot photoread the text again, no worries. Look at photoreading the text more than once as a way of honing your photoreading skills (focus, chant, steady pace, affirmations etc) rather than necessary to the grade.
Alex
