Try playing on hard (rather than vh) battle difficulty level. It does not have that huge effect on morale and stamina (leading to very fast battles on vh), so it's harder to beat AI with single charge for example. AI does more regrouping from routing too. Also AI does not appear any smarter on vh imo considering battle tactics
That's what I noticed from my practice.
As for melee length, you need to change this line in battle_config methinks:
It's the default number right there, try lowering it to 1.5, 1.25 and test if results please you. Beware though I've noticed that lowering it affects cavalry charges (less devastating/effective)
And my best suggestion would be try DarthMod 4b
