joseph, for riddle #1:
i would split them into two groups of five and weigh one. if it equals to 67 grams, you know the delta ones are in that pile and you split that group into 2 and 3, weighing one of them.
if the original 5 only weighs 65 grams, you know they are all alphas and you go directly to step 2 of the first group (weighing 2 or three of them)
am i right? (this is so not my thing!)