Yes he is
And I have a feeling that when it's all over, when he loses "bigly", he will not only blame the republican party for cutting him off, but he will also sue them. He took them to the cleaners by funneling all money he could back into his own business's, and now they are cutting off his money, and he is pissed beyond belief. This man is out for revenge, you can see that by the way he was tweeting his support to his "followers" who are causing problems yesterday when republicans were taking back their endorsements of him.
His followers are mad, and won't be voting for those down ticket candidates on the republican ticket. Trump will continue to go after those who have dumped him, by encouraging this followers not to vote for them. When it's all over, and he loses, all the is left is a lawsuit, something he loves to do, for his last bit of revenge.
The GOP will never be the same after they unleashed this monster on the American political landscape. They will be tied to him for years to come.