Projectors are electronics, which aren't designed for all environmental use. They may be used at nighttime exclusively and the darker the space the better. A slide projector will be significantly less money, but I have no idea what size they can reach without a lamp system which would scorch the slide.

Your size is reaching close to 100 feet or so wide. With a 16:9 aspect ratio that's over 5,000 square feet of screen. In a theater, that's larger than a typical IMAX theater, and will require a projector running upwards of $100,000 for even marginal results. I would think 50,000+ lumens of output are required at the low end.

Generally outdoor digital signage on the large scale is done with LED displays like you see in Times Square, or at outdoor baseball/football stadiums. It is the proper medium for that type of advertising.

Putting the projector inside would protect it. But the window might distort the image a little and you would still most likely need a projector like the one AV_Integrated is talking about.