Doing five highers is pretty intense already, so taking five highers plus n5 maths will mean you are working with more than a full timetable and will make things like assignments/revision/consolidation of work quite challenging. Most uni offers are on the basis of four highers, apart from the most competitive courses. You are better off focusing on getting good grades in four highers and passing n5 maths, than stretching yourself too thin and getting a meh set of grades/not passing your resit. Save PE for S6, it would be a nice one to do then. Speak to your teachers though, they know you best and might have had others in the same situation before.