If dil needs help with English, imo, ds needs to convince her to take a course and help her find one. But that would mean his having to pitch in more. Also, maybe you could babysit while she's in class if you're willing and ds/dil are ok with this.
I know some posters doubt this story is real. But if it is, and if she "cries and gets upset" when "safety" is mentioned, could she have PPD? Or an emotional or learning problem? Ds needs to face reality about this.
But if a word from ds makes her cry, any "resources" given to her by her mil (you) will probably just wreak havoc. Since, again, safety is important, I can see making a suggestion or 2 to ds. But please don't approach dil. I don't think that would end well.