Don't go overboard worrying about numbers.
Generally speaking, having the projector a bit further back is better as it can provide a sharper image. In reality, this rarely proves to be the case, and as you move the projector closer the image gets brighter, which is nice if you need this extra brightness. You should not.
So, I would generally recommend that a projector be placed about 75% of the way back from the closest. In your case, 13'6" to 19'10" means that I would shoot for about 17'10" or so from lens to screen if I could place the projector at that location.
The brightness is pulled from the maximum rated brightness for the projector and will not reflect the post-calibration brightness that this projector will deliver. But, expect closer to 30-40 lumens per square foot from this VERY bright projector. My concern is that after accurately calibrating for color brightness, it may be under 1,500 lumens. This 4 segment color wheel is less than ideal for top-tier color performance.
I'm not sure what you should expect in terms of real world contrast and quality as I haven't read reviews of this model. There is a very long thread on this model at AVS if you want to dig through it for potential settings to help with setup. I loved my BenQ that I used for years, but I'm not sure how the DLP 4K models really stack up. Brightness seems really nice though.