As to the first point, the idea is that some people will make demons that are really good against specific bosses, intentionally or through blind luck, and share the password online. So they didn't hold back on the difficulty of the boss battles because they knew that if a player got stuck he or she could just go online and get a demon or three designed to shred that particular boss. You're right that someone who has mastered the fusion system could just build up their own teams as needed, but Atlus didn't need to worry that most players would not have the patience to get that good.
As to the second, there are two skills with Jihad in the name--you're thinking of the mid-range single target physical attack. I'm thinking of the supreme Almighty skill that comes with a side order of "Debilitate" that hits all enemies. The latter is just "Jihad", the previous has a modifying adjective of some sort. If you want it legally, Shiva comes with it.
