I'm a sevens player, in reality there are different weights that varies between players, but in theory you should be bulked up but fit to the extreme at the same time, meaning less fat, stronger stamina and sudden-sprint skills
Well there isn't a standard size...I guess it's just how you use your build on the field. The Fijian 7s boys are almost always 6' and over and over 200lbs, possibly the same with the Samoans/Kiwis... Also a lot of the 7s players play 15s as well, but they know how to use their speed and skill and are able to adapt what they have to whatever game it is they are playing.
I don't think there is a standard size. I guess, the standard would be around the size of the current England and South African teams. But then check out the Kenyans. I think the sizes are changing.
Not to many pack players play sevens (at the club and college level), too much running around reminds me of flag football. I'd say your numbers are about right but really it comes down to how good of shape they are in.