Well the good news is that your route is for a DONE
3, not -4, so you can already count your savings!
Creating an optimal route really boils down to what you hope to achieve in terms of destinations you want to visit (not just need to visit), mileage or points accrual (or status achievement). Your route is valid, however remember you're only allowed two stopovers in the continent of origin; not sure if that is an issue.
One note is that CX has a nonstop FCO-HKG, so if you don't need to return to LHR you could use that segment somewhere else; a N. America transcon comes to mind. Avoiding a (non-transit) LHR longhaul departure also saves major coin in terms of UK APD.
You don't indicate when your trip might occur. The A380 situation is a moving target; as more come into service other route options might emerge.
As for avoiding fuel surcharges, if you want to book through AA you can phone the AA RTW desk in the US (use Skype or some other VOIP product if the cost troubles you) and see what their tariff office says compared to the online tool; you might find the issue is less a factor than you thought.