My partner with 2 illegitimate kids, the mother is harassing him!

Situation:
My partner has 2 kids from a previous relationship (8 yrs & 4 yrs old). They were not married. He regularly sends support for both the kids and the Mother.

The kids stays with us on Fridays (after school) till Sunday afternoon.

For the past years, he had been giving them 40k+ every month to cover the rent, food and needs of the kids exclusive of the school tuition. The mother is also provided with a car so she can be comfortable. She doesn't have a job.

I've known about their arguments but distance myself since it's between them. But with the recent events, she has been verbally harassing my partner in public places regardless if the kids are there or not. She's using the kids as leverage and acting as if she is the wife.

The problem is we are planning to get married early next year and we are totally stressed with the situation. We both can't work properly considering there's a problem with his kids. He doesn't want full custody as his work demands time and focus. He doesn't argue that the kids will be well looked for in their mother's side.

Is their a legal action in which he can be protected? Maybe stating that he will only support for the kids and not the mother? And maybe prevent the mother from harassing him?

He is not required to support the mother because she was never married to him. His support covers only the needs of the children.

If grabe na talaga, pwede kayong magfile ng civil case pero non-sense kasi damages lang ang makukuha niyo tapos anong damages ba ang makukuha eh wala ngang trabaho.

Remedy: (not legally, just my personal point of view)
- get married the soonest time possible. Have ur bf be bz with your wedding. Tell him to disregard the mother's woes. Just NEVER take for granted or even overlook the support for the kids.
In short, show (not tell) the mother of her proper place. She is nobody is your bf's life. If support is given, it should be said to her that it is for kids.

Thanks sa advice.