sorry, that was my bad with the save DC's. theyre usually 10+half HD+cha mod.

any creature can choose to take the full affect of a beneficial spell. critters with spell resistance can lower it to take a cure spell from a weak cleric, and creatures healed by an element can take the whole lot and refuse to save.

Monster manual on the SRD. the skeleton template states that they are immune to cold. unless its healing them obv :P

with the damage spells always being half necro/half cold... might be unnecessarily penalising the class. if somehow you had a force effect (like magic missile)- it would no longer deal force damage and would besubject to normal miss chances for incorporeal creatures, and many differing spells would have identical effects :S possibly adding the Energy substitution feature to allow you the option of casting as either cold or neg might be a betterchoice... otherwise if a 1hd skeleton walks up to your FN you might have issues.

heres a link for the srd, the monstor manual is built into it, so you can see what undead are like.

http://www.systemreferencedocuments....sage/home.html