If you can't walk away, it pays to stand firm and not take any shit. Remain calm and consistent. Not to rise to any provocations and stay focused on what matters. Only reply to what matters.
Example, he starts going on about "fake media". You don't respond. Just ask your question. Insist on it (Paxman style), or ask for clarification of the reply so that they can't escape it.
Say, you ask about Russia links. He diverts. You follow up with: so, are you saying that you never contacted Russia pre-election? Repeat as necessary.
As for his minions in the WH and Congress, they need to stick together and exchange notes. They need a united front.