Negative scale-free topology
Whenever you have batch or other nuisance variables driving variation you're going to get odd networks. You tried using SVA, which is a good method to use, but it seems in this case that it's able to optimally handle this dataset. I also strongly suggest that you use pickSoftThreshold() to choose a softpower, since that may produce better results (though since you already have negative values I'm not holding by breath). In general, you're going to need to play with either SVA or filtering to remove the batch-related genes that are causing problems.