After the Geneva talks, they could simply withdraw from swift, close their borders to western carriers, dump any remaining debt, close their airspace to western carriers then adopt a defensive military stance, because they CAN defend themselves militarily, but the west probably CANNOT defend itself economically.
It strikes me that Putin may have a list of options in front of him along the lines of the above, the west may know about them, but which options he will pick from the list and which he will not, will be information that is inside his brain only.
This seems the most rational approach to me.
Militarily, I am not sure what he can do that would not simply feed the beast. Surround the US with nuclear subs? Nobody knows where they are anyway.