If you haven't tripped the breaker yet then that's a good thing , but long term continued use will eventually have an effect on the breaker. It will become weaker over time and eventualy will start tripping with less power draw.
Try talking to the maintnence person and see what info you can get for your apts electrical system.
Using one outlet is also not good and when you have a lot on if you put your hand on the outlet I'll bet you it's warm or even very warm. The outlet plug can also get weak and brittle over time with high useage.
Your power supply will only draw what it needs and even though it's 1200w it doesn't draw that, you can use one of the free power calcuators to see what your things ae drawing from the psu.http://extreme.outervision.com/psucalculatorlite.jsp
You can also see if there is a possability of adding another outlet , but that might cost you and it would depend on what your long term plans arer.