Vicar step back a minute. Relationships with parents are a curious beast and as children enter adulthood, it can make for an awkward transition. In terms of DDs comment there are many possible interpretations of that. Sometimes a certain detachment gives us more space to be a different person and as we grow, whatever age, these relationships come and go, change.
Soooo embarrassing. That's a tough comment but I can remember being mortified by the 20 questions from my Mum and her 'concerns' because I was not interested in having a boyfriend or showing any great interest in guys. That embarrassed me. Or the insistence that I should dress less conservatively (taken me twenty odd years but yes she did have a point and I greatly admire her style now!) and present myself in a more physically attractive way. Or that I was more outgoing... Maybe seems odd to be embarrassed by these things. Maybe it is me after all 
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Don't dwell on her comments too much. I am not sure how to suggest handling them - is she emphathetic or mature for her age? Could she understand that perhaps you felt hurt, not in a way to lay on guilt, but more as a way of understanding?
Her comment about BF's Mum. If you like the family, this is a good thing. It doesn't necessarily take away from you but allows her to grow in a different way. Children grow up and out. You have helped her develop those skills. And I know you are proud of her. And you should be proud of you too.
DS. It is hard and frustrating. You are doing a tremendous parent job and although there are areas where it will always be hard for him to cope, you have also helped him grow so much and supported him.
My bottom lip wobbles a bit. These years are still to come in our little household... They will always be your children, no matter their age, and this adds a duality to the relationship. Children to be protected and nurtured but adults to be independent and responsible. It is hard. I now look back and admire my parents (flaws and all) for the amount of space they did give me and trust. It's taken me a loooong time to realise that. Maybe I should let them know.
Also be gentle with yourself and take care in how you respond emotionally. There has been a lot going on and still going on. More recently I have been trying to take time out before I respond to things, to give dust a chance to settle and to try to find the rational response. It is part of my ongoing exercises to keep an even keel. I don't know if that will help but hopefully you will find answers that help bring you some ..... relief, peace, calm.... Let it go.
PS I have never seen a rat pet, and I (with shame admit) am prejudiced against them simply by mental association to allsorts, but your descriptions of them have made me rethink (although not reconcile) them as pets and animals.