Yep, the game manual also suggest the use of pause, pause and pause....IMO, no ways you can do it efficiently with wars on all fronts without pausing it.
I recently decided to switch to the expert difficulty after playing with normal difficulty for awhile and it's been alot of fun, more actions and more hoplites to fight with ;)
Lamia is a good training ground for my phalangites to gain experiences, a phalangites with a good heroic skill general attached can easily crush 2 hoplites brigades.
I think you can switch to another difficulty any time in the game without restart a new one.