I’m sorry, there are still no proper tutorials for the connectivity analysis.
With the options you selected, you are trying to compute a connectivity measure for 15171x15171 pairs of signals (all the source signals). For the coherence frequency resolution you selected, this requires the creation in memory of a few matrices of about 200Gb. This is not something you can do on any computer.
If you want to compute a full connectivity network for the whole brain, you need to decrease the size of the data you generate by using regions of interest instead of all the source signals. Ideally, you should base all your computation based on your hypothesis, which should be something relatively specific (for instance “the connectivity between region A and region B is higher in condition 1 than in condition 2”), and compute only the measures you really need.
Then you can compute this one single measure for all the subjects and all the conditions, and test for significance with non-parametric tests.