I beat it on hard...
strategies that don't work:
+4 demon for every 4 cost (if you remove the four cost with the hungry 1 power, it doesn't stack but lowers back down uggghhh)
most other demons
strategies that work:
chainsaw demon is required. Note that this demon won't work unless surrounded prior to casting.
What I did:
on the 1 and 3 cast the best demon you can find (11 solo demon)
tally: 22
on the 2, consume the 1 and 3 demon with the 1 power
tally: 23
on the 4 and 5 cast the 1-shot demon (17 power each)
tally: 34 + 23 = 57
on the 1 and 3 cast the chainsaw difference demon (5 + differences)
tally: 2*[ (5-1) + (17-5) + 5] = 42 + 57 = 99