Back in the day when i used to lift alot and work out with personal trainers, the one thing I remember them saying was that abs are the one muscle group that couldn't be over trained. IMO sit ups, crunches are fine. The other exercises are probably also OK given your quantity.
From an MMA perspective, Liddell's book pretty much sums it up. MMA is not about strength, but strength over time..
What does he mean by strength over time?