Hi Summer,
Big hugs to you. Motherhood is a stressful journey. I hope writing the post helped you destress a little.
It helps to keep in mind that different children have different developmental curves, so do not be too stressed if your baby does not fit on the 50th percentile line (<- easy to say, but hard to implement

). As long as she is growing and you can see that she is learning new skills, like sitting up, crawling, standing etc, she is probably fine. I'm sure that since you interact with her everyday, you will know when something is not right. Hopefully this will help you be more at ease with the staff nurse's comments.
Don't worry about the not mimicking. My kiddo didn't mimic us at all, until very recently. So like those examples of sticking out your tongue so that they will stick out theirs when they are an infant, it never happened with us. We mimicked her instead! Perhaps she found that more amusing. Its not until a month or so ago, when we noticed she started mimicking our actions, like carrying grocery bags, or trying to wear our shoes. For us, our kiddo is on the small side, so sometimes the healthcare professionals will say things like oh, I will prefer if her height is on the 10th percentile line instead of the 3rd percentile line. And we just roll our eyes, because its not like we are trying to stunt her growth, and how else can we make her grow? Put her on a stretching machine?! At the end of the day, she is gaining height, so its okay.
So I guess I'm trying to say that at the moment when we find out that our kids are not fitting the growth milestone and we cannot check the box in the health booklet, we get worried, but eventually find out that its okay.
As for the eating, it could be that your baby is not very interested in solid foods. But at this point, a lot of her nutrition still comes from milk, so its okay. Perhaps you can try involving him at your meal times, so that she sees you eating, or you can increase the number of solid feeds, like some bread for breakfast in the morning, then fruit puree for teabreak. Sometimes it could also be the type of food, like my kiddo didn't like those rice cereal at all! And also didn't like congee. Instead, she pretty much started with rice.
As for your mother, I'm sure she is trying to help and doesn't realise the stress that she is adding on. I'm not sure about how your relationship and dynamics with your mother are, but perhaps you can sit her down, and nicely tell her that there is a set time to bring the baby out, as the baby has fixed timings for naps. She may say something like, "but last time you (and your siblings if any) was/were not like that", so remind her that each child is different, and you are the mother, and the one who has to deal with the crankiness. So if she really wants to help her daughter and play with her grandkid, please follow the guidelines. Everyone will be happier for it.
As for your frustrations with your husband. If the main issue is the state of the house and how you have different standards of cleanliness, it is indeed a frustrating one. If you both are unable to find a compromised in between your cleanliness levels, is it possible to employ some cleaning help? Like perhaps a part time helper? So that at least you do not feel saddled with all the tidying up?