Few simple things to add..
1. Get the blue armour from going to the lake, bottom left, walking onto the little bit that sticks out, pressing space when facing the lake, and choosing to throw the panties in. Then beat the Hydra that appears.
2. You can get Excalibur (with good alignment) from the statue in the center of Castle Town.
3. Get Death from the girl in Castle Town who talks dismissively about Nova, AFTER you've beaten Cerberus.
4. The labyrinth after completing the main quest seems simple.. carry on through the dark doors at the top till you hit grass, then turn right.
5. Protip : Elixir. Buy it from the potion merchant in Castle Town, restores HP and MP to full.
6. I believe the evil sword revolves around the black gravestone in Village, but it requires lots and lots of evil alignment.
7. There's a Temple of Thor, which gives you quite a nice hammer, top right corner. Just walk across the river.
8. Magic doesn't seem to affect Cerberus. Get a higher strength

. HP is good too.
9. Cure is surprisingly powerful as a healing spell.
10. You seem to get Nova as soon as you have enough MP to cast it. Seems broken.. need about 300 MP or so.
Oh, and Astaroth IS the last boss, ne?
Good luck!
P