You have a pretty good handle on it,but I would suggest:
Try to visualise the process in your head,write down the steps,hand draw a block diagram.
The LTspice simulation schematic is messy & has additional junk which is not necessary for an understanding of the process.
( But,then again,I
hate simulations!
)
"To demodulate the SSB signal we have to multiply it with the BFO's output (same frequency and phase with the carrier)."In most SSB applications,the "BFO's" phase relationship is not important.
In fact,it's funny you should mention BFOs as these were normally free running tunable oscillators incorporated in early Communications Receivers to provide an audible note when receiving keyed carrier Morse Code transmissions (commonly,if erroneously,called CW).
With the advent of SSB,these were used to provide a local carrier to allow demodulation,which they did quite well,considering their simplicity.
More modern designs use a fixed local carrier,& shift the received signal in the IF passband to adjust for best intelligibility & most natural voice.
This local signal is still not in phase with the original carrier,though.
It is possible to phase lock the local carrier by not reducing the original carrier to zero,but instead transmitting a reduced carrier.
This is most often used in RF systems that use ISB--two sidebands with different information.
PS:There is something weird with your last waveform--if this is after the demod,it should be the same as your first one--a 1kHz sinewave.