If you consistently see 110% there is something wrong with your proctor. Especially if you are using a modified proctor. Still although it is not uncommon to go above 100% of a standard proctor, equipment is better than when that test was designed, doing so consistently is cause for concern...
I don't know exactly what you mean by "muck", but I wonder if over excavating the footers and backfilling with gravel or better soil would be an option. If you are building in a building pad I assume you are elevating the pad so your original ground will need to handle to bearing...
How critical compaction is depends on a number of items:
1. what is going on it
2. what material are you compacting
3. what is the thickness of the poorly compacted layer
4. what is the thickness of the overall fill
5. what is the depth to bedrock
Where I work we deal almost exclusively...