I am southern too and we say "bless his heart" as an insult. Like "bless his heart he is nice but not too bright". One day I was having the worst morning: spilled coffee on myself, tripped and bruised my leg, something else. My mom sent me a text "well bless your pea picking heart". I laughed so hard I put it under my mouse pad at work (have one with a clear cover). The bless his heart reminded me of it.