You can overenroll if you have a good reason to do so, but if you planned on taking all the subjects at the same time, doing that many subjects in your first year could be detrimental to your marks.
I, too, am meant to be taking Physics: Fundamentals but I'm in a different situation to you - I've already taken both Psychology subjects so wouldn't be doing 5 subjects in the first semester (I'm taking it for the GAMSAT too

Unless you're planning on completing one of your breadth subjects at a later date, they might not allow you to take Physics because you will overload your timetable. Would you take one of the subjects in the summer semester? Perhaps a breadth subject, to make up for the lost window during the semester...
125 of your credit points may be Level 1 subjects, so if you use up 12.5 on Physics then you will have to do more Level 2/3 breadth to make up for it. That's not too big a deal, though. At least I don't think it is!
As far as I know you don't actually need CAP to do your extra subject if you sort out your study plan properly, because it is a first year subject and you're allowed to have two extra level 1 subjects anyway.
I would talk to someone at the EPSC which is what I did today. She just told me to wait until my credit was approved and then come back though - uber helpful.