Do ant colonies prioritize survival of particular members above others?
I couldn't find any information about ants starving in times of plenty, most likely since it's difficult to determine whether an ant colony is "letting" certain members starve or whether the ants have just died for whatever reason. To your second question, though, yes! This paper, The Effect of Colony Size and Starvation on Food Flow in the Fire Ant by Howard and Tschinkel, shows the effects of different lengths of starvation on the passing of radioactive food through different sized ant colonies. First, the queen:


  Generally, queens received radioactive food earlier in starved colonies than in well-fed ones


Starved foraging ants distributed food more quickly than forager ants who had not been starved:



And interestingly, in large colonies, larger worker ants were more likely to receive food (radioactivity) than smaller ants. Very cool paper.