A photo of the actual room.

Given your room width, You might want to consider installing in-wall surround speakers. There are plenty of manufacturers that make high quality in-walls. Hiding them is more of an aesthetic preference of yours. If you hide them in columns, that will take away room width; in a not so wide room.

Screen size sort of depends on what aspect ratio you're looking to do? 16:9 or 2.40:1. You can probably get away with a 10' wide screen in either aspect. Projector/lens throw ratio is also contingent on the screen size and lens ratio.

Viewing distance also depends on your screen size.

Ideally an equipment rack should be placed outside of the room. Equipment racks produce heat. To make sure you don't have hardware failure from said heat, you need to ventilate the equipment. Using fans in the rack to ventilate is fine, but that produces noise which you don't want in your theater; hence place the rack outside of the room. If the rack must be in the room, there are other ways to cool it with ducting systems. If in the room, you don't want the rack to be visible from your viewing angle. Equipment in racks typically have a bunch of little LED lights which can 1) be distracting when you're watching a movie & 2) produce ambient light which will detract from your movie image.

As far as sound is concerned, you want to try to eliminate as many hard surfaces as you can in a theater. So yes, I would try to get rid of as much glass as possible in the room. Not to mention, glass reflects light; which again creates ambient light and detracts from your image quality. Darker rooms are ideal.

Hope this helps getting you started. If you need help we offer theater design services. And depending on location, install services...