Rep. Max Miller isn't touching questions about his personal life amid his bitter custody battle with ex-wife Emily Moreno and public feud with her father, Sen. Bernie Moreno ... going silent when pressed about the family drama.

We caught up with the Ohio congressman in D.C. Monday, where Charlie asked how it felt to be back amid everything going on in his personal life ... but Miller didn't bite.

As we've reported, Bernie has publicly branded his former son-in-law a "danger" to Emily and called for him to leave Congress, while Miller has claimed he has dirt on the senator.

Miller also kept quiet when asked if he's concerned about his November race.

Things got even more awkward when Charlie asked about Miller's supposed dirt on Bernie ... specifically why he has it, whether he plans to expose him under certain circumstances, or if he's taking the secrets to the grave.

Miller sidestepped the questions entirely ... instead asking reporters if they had anything for him about the House Ways and Means or Foreign Affairs committees.

Check out the video ... Miller finally opened up when reporters turned to the nearly $40 trillion national debt, calling it a big problem and saying both parties continue to contribute to it.

As you know, Emily has accused Miller of abuse and endangering their daughter during their custody battle. Miller has denied the allegations.