Here is a link to the calculator with the VW50 already selected for you. It's still there for use in the calculator but it's further down the list under discontinued projectors.
http://www.projectorcentral.com/Sony...ulator-pro.htm
As you can see, this would work well for you if you want to use that mounting place you have 12.5' from where you want your screen. For best results it looks like you would want a screen of 100 - 120". Being in the green zone for brightness is mostly just a guideline as how much light control you have plays a big part of that. I wouldn't ignore it completely though.
I have heard that the VW40 is just a replacement version of the VW50 and I believe the basic specs (zoom, contrast ratio, brightness) are probably the same, but definetly compare the specs to make sure before buying it. For that matter I think the major difference between the 60 and the 50 is that the 60 has better contrast. I looked at that in the calculator as well and the zoom is the same at 1.7:1
As far as the price difference being worth it, I can only tell you that I'm very satisfied with the picture I get from my VW50 and I wouldn't expect much difference in the VW40. I've never actually seen a VW60 in operation to compare the two directly.
Edit: Here's a link to a review on the VW40. The review doesn't do a comparison to the VW60, but it does give a comparison to other projectors in the same price range from Panasonic, Epson, and Optoma. Hope that helps.
http://www.projectorcentral.com/sony_vw40_review.htm