In general, most US physics programs do not conduct interviews before offering admission. Generally, if a school does contact you about an interview, it is more of an informal discussion with a potential PI about possibly joining his or her lab.
As for your question about your scores, it depends greatly on your individual demographics. If you are an American citizen, a low PGRE score doesn't necessarily disqualify you from being admitted from a program (though it certainly doesn't help). If you are not a US citizen, a low PGRE likely means that you will be wholeheartedly rejected from the majority of programs. Unfortunately, the standards are far higher for international candidates.
Another note of importance, in general the PGRE is far more important for physics grad school than it is for astronomy grad school. As such, if your other credentials are up to par, it is certainly possible that you can still be admitted to high quality astronomy programs with a mediocre PGRE score.