IS THERE ANY LEGAL WAY AT ALL OUT OF A SUBPOENA TO TESTIFY IN COURT?

I got subpoenad to testify against my ex husband from years and years ago, he was a walking nightmare, the first time he hit one of my kids I left him unfortunately he did bodily injury to my son and I was able to get a felony child abuse arrest for him and he later plead guilty to a lesser charge allowing him to serve a 5 year deferred sentence and it was expunged off his record. Now he is at it again with another woman's children and the father has launched a custody battle against her and my ex husband; according to the father's lawyer since the charge was expunged they can't bring it up in this custody case without having me on the stand. This guy scares me to death, I don't want any part of this and don't understand why they need me if he is abusing a child? Is there any way I can get out of this, I sincerely fear for my life and the life of my children if I testify against him and I have expressed that but they don't seem to care. I spoke with a judge who has dealt with my ex husband and he told me to get home security, he will rewrite the protective order and in his professional opinion at all costs try to get out of this, he said he always felt uneasy around my ex and is surprised he hasn't made headlines yet. This is very disturbing to me!