Need some stepmom advice

My fiancé and I had his kids dropped in our lap about six months ago without any warning and I’ve done everything I can to make sure they feel loved and welcome in our house since then but things are starting to get out of control. My SS who’s four has very bad ADHD, anger issues and behavior issues so disciplining him is almost impossible because he just screams or laughs in our faces. My SD who’s six is high functioning autistic but that’s a challenge in its self with her sensory issues and not being able to understand that the things she says sometimes are extremely hurtful to people around her. We put them both in therapy and are trying really hard to understand what’s going on with them since Bio mom was abusive but it’s starting to seem more like they just don’t care about how some of their actions affect both me and their dad. I also have a 2 year old bio daughter who’s starting to learn their behavior and I just gave birth to our son three weeks ago.

Recently my fiancé’s mom who I’ve never had a problem with and actually have a good relationship with started saying that I don’t comfort my SK’s in public, that I compare my SD to one of her cousins who has worse behavior issues than she does and that I’m more attentive to my daughter than I am to the other two which is not true at all but then in the same breath told me how amazing I’m doing at supporting my SK’s. I grew up with step parents so I’ve been trying my hardest to make sure they don’t feel left out in anyway but now with all that being said I’m starting to think I’m not doing enough despite the fact I quit my job and have been trying the best I can to be a good step mom for these kids.

I do know I’m a little more attentive to my daughter and now son because they are both under the age of three while the other two are able to somewhat entertain themselves.

I really am trying to make sure they are all treated equally and loved the same. But his moms comments make me feel like I’m still not doing enough or that their behavior is because i love them differently than i love my own kids.

Does anyone have any advice for this?