OP - It is very odd that one individual is in communication with what they think is the CEO's office over several bookings at one time. My suspicion is that you are simply dealing with people who are fobbing you off by telling you this and that all of this is causing massive confusion, delay and will ultimately harm whatever it is that you are looking for out of all over the various traumata BA has caused you.

As to the specific, your options are to make a claim under EC 261/2004 for 75% of the value of the ticket (CWS notes the ticket vs. segment issue), which will amount to avios + some cash. You will then have avios + cash to spend any way you wish. You may also choose to negotiate with BA for whatever the two parties are willing to offer and accept. This appears to be a situation where there is something eminently reasonable which you want and which BA could offer. Customer Service ought to be able to sort this in a quick phone call.

As to the broader issue. Flights get cancelled for many reasons. It is hardly in BA's interest to do so, especially so close to the time of the flight. You were rebooked relatively immediately and I presume could not be rebooked into F because there was no space. Just one of those things which happens when one flies long-haul.