The salomon looks like a good boot but with 100 flex and his weight there is no way he is going to be able to handle that boot. You should be looking for something around 80 flex in my opinion. If you're serious about skiing then you may want to take a ride to surefoot (expensive but custom) in the city since ski stop and snohaus don't seem to have what you're looking for. Also, rarely if ever will someone be able to buy a boot off the shelf and have no issues. You will probably need the boot blown out in some spots, punched in others, etc. Sadly ski boots and pain come hand in hand for the most part.
P.S: Always buy the best you can afford when it comes to boots.
Little knowledge for you:
http://www.skis.com/docs/the-differe...ens-ski-boots/