I would wait until your friends parents return home and leave it up to them to support him.
I suppose it depends on how close you all are though, do you see them both often? Are you close to both of them or only him? Or are you more of an old friend, an acquaintance?
If he is guilty of DV, be careful he isn't involving you to try and make his wife second guess the dvo over jealosuly. DV perps do strange things to try and get their partners back.
No we don't know what happens behind closed doors and even some of those that do know DV is happening, choose to ignore it and not get involved, or refuse to face that their friend or family member is like that.
On the other hand PND may have been what led her to take out the DVO.
Or it may just be his excuse as to why she has taken it out, maybe she doesn't even have PND. Or she may have PND, but may also be a victim of DV. We just don't know.
There are some women (no doubt men too) who take DVOs out on false allegations.
Usually they do it once the relationship has already ended though and the couple has gone their seperate ways and they are wanting full parental responsibility.
Usually there is a new partner involved and they want only him to be the father figure, or they may want to relocate overseas or interstate knowing the other parent wouldnt agree to not seeing his children on a regular basis, so need that full parental responsibility so they don't need his prior written approval. Sometimes it's because the father has a new partner and the mother of the children has jealously issues so doesn't want the children around the new partner.
In your friends case we don't know if anything is going on like this, but since they were still together and living together that same day, then it isn't likely.
The DVO can change his time spent with his children, in the way that if she does get it approved, she can now choose to apply to the family court with it, and seek full parental responsibility, it doesn't mean it will be given though, but if so, she is solely responsible for any life changing decisions then and he will have no say, for example, where they live, go to school, obtaining passports, travel, religion, Drs etc plus it could mean less visitation an6s supervised visits either in a contact centre where a stranger will watch him with the kids, or via a court approved other family member, like his parents, or even hers.
However there are couples who have a dvo then continue on with their relationship.
All he can do is plead his case, provide any evidence, phone records, his history, the medical issues happening, letters from the hospital, Drs etc.
It will probably be adjourned when he first appears, the Judge will ask for any witnesses to appear at the next hearing no doubt. If he decides not to go to court, the dvo will be granted.
As you don't know for sure if he is innocent or not, i would be very cautious and wait until the parents are back to offer him that support if it were me.