I also think we need a little more details..... and that really doesn't have to a multi-pager....
But so far I see (before flying):
- downgraded 1 segment for 1 passenger on OZ
- downgraded 1 segment for 1 passenger on SQ
And some problems during flight due to your arriving flight being late:
- a downgrade on an alternative flight
- you luggage got lost
Makes me wonder why you accepted the changes knowing them before flying. I would think that you could have done something about this before flying? I doubt you will get any compensation now.... as long as not all your segments are in C you have to pay the F miles.
For the operational problems you might get something. And for your luggage there is the standard coverage, supplemented by your insurance.
Doesn't sound like a great trip, but most could have probably been rectified before flying.