Redefining the strategic goal as unifying Donbas is probably his best cynical path out. If the EU holds the line on gas, once the ammonium fertiliser stocks run down he has a scary secondary lever to pull (postwar agricultural dependence on ammonium fertiliser worldwide is huge and the primary feedstock is gas)
Grieving mothers might yet be his downfall, but I doubt it. The horse has been whipped too long to kick back.