About 6 weeks ago I booked 2 return flights on KLM to JFK from LHR in September using my FD points. I have paid 50000 points(each) and now received 2 economy tickets. I had considered buying economy tickets and using FD points(40000) to upgrade to wbc but cost was too high then(£600). However there are now tickets for sale on Air France for £297. I am now considering cancelling my current booking but have the following questions(which is probably too much for the average FD helpdesk employee) after some research:

1. I paid @£120 in tax for my flights; if I cancel do I lose this money?
2. The AF flights are only available at £297 on Expedia/Ebookers etc not the AF website; does this matter ref. business class upgrade?
3. How can you check whether AF are offering free upgrades on a specific flight before I book the economy tickets?
4. What is the process for using FD points on AF flights; do you call KLM helpdesk or AF?

Any other tips/ things to be aware of?