Now it's time for diplomacy. Just accept the fact that the majority of Donetsk and Lugansk want to be an independent state and negotiate the borders in peace, instead of trying to further escalate.
There was already a precedent in Kosovo, where one-sidedly proclaimed independence was accepted, and a sovereign country that tried to prevent it was crushed by NATO military until they had to accept “the new reality”.
And now let someone tell me what is the difference between Ukraine-Donbas-Russia and Serbia-Kosovo-NATO situation? Except the facts that NATO now sides with the sovereign state instead with the separatists, and that Russia is an enemy of NATO.