On point C3), I think that your correlation could be interpreted as “people with mental illness have less time to engage in activities” rather than EA having an effect on mental illness (one way to test this would be to compare the correlation of several other social activities in addition to EA and see if they all follow the same pattern—if they do then maybe this is really a proxy for peoples’ ability to engage with social activities rather than anything unique about EA). But, since your p-values so large, I wouldn’t trust this result to have explanatory power with either interpretation.
On point C3), I think that your correlation could be interpreted as “people with mental illness have less time to engage in activities” rather than EA having an effect on mental illness (one way to test this would be to compare the correlation of several other social activities in addition to EA and see if they all follow the same pattern—if they do then maybe this is really a proxy for peoples’ ability to engage with social activities rather than anything unique about EA). But, since your p-values so large, I wouldn’t trust this result to have explanatory power with either interpretation.