for probably the best explanation of LWF(linear workflow) have a look here: LINK
I set up your scene quickly with a vray camera with adjusted exposure. A vraysun for direct light shining through the windows. For the light outside the window I put a vray plane lights outside each window and set them to skyportal. My Max system gamma is already set for vray. Irradience map as primary GI engine(although I would set this to brute force for final renders) and light cache for secondary engine.
Lastly, and most importantly, to completely get rid of the weird blown-out spots on the windows/curtains/clock, select the wall geometry and the ceiling geometry and apply a shell modifier. And also, move any geometry that intersects the wall(the clock)
Having done all this(which took no longer than 5 mins) the white spots where completely gone. Any other noise/blotchiness will be down to your image sampler and GI settings.