NEW YORK — Everything’s bigger in Texas — including the twists in John Lithgow and Douglas McGrath’s new off-Broadway play. The duo insist that no matter how surreal some parts of “Everything’s Fine” may seem, the one-man show depicting McGrath’s whirlwind experiences as a teenager in West Texas is completely legit. “It actually happened in real life,” Lithgow, who directed the show, told the Daily News. “I mean, honestly, people come up after the show and say, ‘Well, surely this can’t all be true?’ And it’s all true.” Opening Thursday at the DR2 Theatre near Union Square, “Everything’s Fine” …