Thanks for compiling this list. I think it's hard to aggregate impact and effort into a single metric, since the latter is hard to measure and varies considerably across individuals. In this case, I would have found it more useful to have a ranking ordered by impact alone, and then decide on the basis of this ranking and my own sense of the amount of effort required by the different interventions. (Cf. Holden's post on "rational" vs. "quantified" approaches to cause evaluation.)