“If I am not mistaken SLS (Space Launch System) is a NASA project not a Boeing project.”
It is, but it will be obsoleted by the SpaceX Starship.
“And again IIANM SpaceX’s Big Falcon Rocket is the backup plan for SLS.”
Not the Falcon Heavy, but the Starship.
SLS is obsolete. And many years behind schedule.
I disagree and it is not many years behind schedule. It is pretty much on schedule. Now SpaceX might make it obsolete, but that has not yet happened.