You might consider moving the PageUp... Backspace block a little to the right so that it aligns with the rest of the keys. Also gives you a tactile difference your fingers can detect.
Also, if you wanted to try out the layout (with, alas, rubber dome switches) you could look into a Cherry G86-61410EUADAA POS
keyboard.
http://cherryamericas.com/product/spos-small-point-of-sale-keyboard/* Look st the ones without track pads.
* Some are less than $60, including shipping, on eBay
* 1 more row at the top than your design
* 4 more columns (numeric pad) on the right
* Programable (changing key mapping, I think. No layers-like functions)
* They are very flat. You'd have to put something underneath to set an angle
* So, too many keys. Larger than your design. Could be useful to see if your layout works for you without designing a PCB, case,...
Cheers!