-5 chaos mean "5" or "-5", chaos "base value" is 9, so it's 5 (9-4) or -5 (9-14).
if it's the first the reply is no, you must remain under 5 for chaos and damage for the full RP bonus and don't waste DF in repair (if you cannot go 0 or better with the 'free' bonus after the battle you mus spend a bit to reduce them, i strong suggest to strive for that solution, if you cannot reach 0 in one stat spend 10 DF in reduce it isn't a high price), it's the second it's an absolutely overkill.
this is the result of my most optimized game:
Victory Points: 17
Chaos: 2
Collateral Damage: 1
Enemy Forces: 29
Army Size: 35
Army Quality: 14
Acceptance: 23
and it's enough to hit any best threshold for the rest of the game.
no, it's the only DF petition you cannot delay in successive iteration.