There really should be a way to improve energy pool/regen. Just 200 as final total gives you 3~4 first chapters or 3 battles at advanced ones. I understand this low amount for anti-shuffle abuse, but, at least, the regain should be better (half energy refound on victory, maybe?)
I had no problem to beat the last level following BennyGreen's combo, but I changed the ground a little bit, as it follows:
S - S - I - S - B - A - A - A
S - I - S - S - B - A - A - A
S - I - S - S - B - A - A - A
S - S - I - S - B - A - A - A
Spike, Ice trap, Barrier, Archer
I liked the ice trap, as it is really handy against big enemies, and there are a LOT of them in that level, so the archers hit the slimes, ghosts and bombers instead of them. I also recommend the 3-stars saver regen skill.