Kremlin has said multiple times, that use of western weapons against targets on Russian soil will be escalation and they will target NATO bases.

There have been multiple strikes using western weapons on Russian soil... with zero response. One of the most recent being shooting down an Il-76 near Belgorod.

I think Putin can find a way to exit the Ukraine and define that as a success if he wants to. But he still thinks he has a chance to win on the battlefield, so he has no motivation to do that.