I echo the above, plus...

HKG-NRT is far superior to HKG-NGO due to the Kaiseki meal in F (make sure you do get on CX504)

I would go HEL-TLL by ferry not plane - it will be quicker (city centre to city centre), probably cheaper, and some variety!

If the commas are the stopovers and the rest are for miles then you could do better with the mileage maximisation in NA at both ends of the trip (e.g. LHR-SFO-DFW-DCA)

Enjoy the trip!