Hi and welcome to Discuss Cooking
Do you have a water-tight container large enough to hold the block? A large cooler? Oh, just occurred to me - do you have a bathtub?
Put the block in the container or bathtub and fill it with cold water. As the breasts on the outside start to thaw, remove them from the block, dry them off and repackage. The water should stay quite cold, but if it starts to warm up, scoop some out and replace with more cold water.
I have no idea how long it will take to separate that much chicken, but you don't have to thaw it all the way - just enough to separate them. Hope this helps.