Hi,
To be honest, I think the 1 hour 15 min connection time at YVR is a bit tight for comfort. ( the BA flight will board about 40mins prior to departure ( the lounge being by gate D64)
Instructions for connecting pax at YVR can be found here;
http://www.yvr.ca/guide/around/conne...asp?id=usa2int
( you will have to fill out a canada customs form)
2. 4K is an ok seat on the 747 but you are closer to the galley and you have 4F across the aisle ( Row 3 or Row 2 would be better still IMHO)
3. Very doubtful that BA will allow you to walk on to an earlier flight to CPH.
If possible I would try to get on an earlier AS flight to YVR.
Enjoy BA F!
Regards
TBS