I agree also on the use of flight coupons in SE Asia and S. America.

Iguazu Falls isn't served by any OW airlines, so that part should be planned as separate air tickets or an overland jaunt. There are airports on both the Argentine and Brasilian side of the falls, so one thought would be to save OWE coupons by flying AEP (domestic airport in Buenos Aires) to IGR (Argentina side) then IGU (Brasilian side) to Rio or Sao Paulo. Then use your first coupon in SA to get to Lima for your Andes/Bolivia bits. Domestic and ground transport in that area will be a more effective use of your resources, followed by LIM-SCL or LPB-SCL, then Easter Island, then onward.

For example, MAD (IB) EZE (surface or AEP) IGR//IGU (domestic/surface) GIG (domestic/surface) GRU (LP) LIM (domestic/surface) CUZ (domestic/surface) LPB (LA) SCL (LA) IPC (LA) SCL > onward. (4 OW coupons in bold.)

ATH-IST is around USD200 or less, so I would also look at an open jaw there too, which would give you a whole second round-trip in Europe rather than using 2 coupons zigging and zagging. Russia? Morocco? Scandinavia? Numerous possibilities.