haha i am really having to read the book in depth to get clear on all this now!
Firstly I must apologise for an error on point 4... you were correct and I was completely wrong, the thrust going to TOGA at A.floor is in fact an autothrust function!
Quote from FCOM DSC-22-30-90-A/THR ACTIVATION
"When ALPHA FLOOR is activated, regardless of the initial status of A/THR and the position of the thrust levers, the A/THR activates."
Next, the FACs do talk to the ELACs.
Quoting FCOM DSC-22-40-10-GENERAL
"Each FAC interfaces with the elevator aileron computers (ELACs) when the APs are disengaged, or with the FMGS when at least one AP is engaged."
Next, the book is slightly unclear whether these FAC calculated speeds (V.a.prot and V.a.max) are sent to the ELAC for use... it seems to suggest not, but i am certainly unaware of any capability of the ELACs to calculate these speeds themselves.
Quote from FCOM PRO-SUP-10-PROTECTION SPEEDS.
"Vα PROT, Vα MAX and VSW are computed by the FAC, based on aerodynamic data. They are only used for display on the PFD, and not for flight control protection (the activation of the protections is computed by the ELAC)."
More on A.floor, Quote from FCOM DSC-22-40-30 ALPHA FLOOR PROTECTION
"The FAC sends this signal (for A.floor) when :‐The angle of attack is above a predetermined threshold, that is a function of the configuration.‐In CONF3 and CONF FULL, this threshold decreases as a function of the aircraft deceleration rate (down to – 3 °)."
does that go some way to answering your questions?