Your DD needs to be assessed by a psychologist.
She is functioning emotionally and socially at the level of a child aged about 4/5.
Academic functioning is a red herring here. It only shows she is intelligent (but that is evident from her threat to report you).
Her behaviour in school otoh holds some evidence as to her issues.
Holding the teacher's hand at the head of the line at age 6.
Arguing with a peer about who is 'top girl'.
Clashing with cousin of the same age.
Complaining of having no friends.
Low to no tolerance for frustration in her work.
Low to no tolerance or ability to solve problems in the conduct of her daily relationships (shown in her school problem and in her acting out at home).
Doesn't get jokes.
Low understanding of other people's physical reality - play fighting, tickling can get out of hand.
Plays with dolls with her little sister. (This is an issue in the context of problems getting on with and forming relationships with peers, not in and of itself).
Sits out peacefully with elderly neighbours. (Same as above - can cope with undemanding, predictable social situations).
You say you can see red flags appearing when she is about to kick off ('attitude developing', frustration evident if she loses a board game).
However, I think you could use other flags earlier as a hint that you need to provide an opportunity to connect with you:
Sucks her thumb. (This is again not a problem in and of itself).
Behaves like a baby needing attention. (Again not a problem per se, just in the general context).
When you see or hear these indications, a cuddling session or some other physical contact might head off a playfighting session later on that gets out of hand.
I agree with BlackEyedSusan's thoughts here, and her suggestions of sensory aids and attention to sensory needs not currently being met - a weighted blanket, physical touch - hug/cuddle/hands on her shoulders that she can come to rely on getting if she asks for it.
Imo, your response, more specifically your husband's response, to DD and the fact that she knows you are not on the same page in dealing with her behaviour, is actually a huge contributor to the problem that is at the base of this. There are some things you could try at home that would do no harm whatsoever, and might even result in some mitigation of the behaviour you are all suffering from.
The feeling that she, the child, is in charge, that there is no way to gauge where the boundaries are contributes to massive anxiety in children on the spectrum to any degree and also in NT children.
Your H needs to pull the finger out. You and he need to learn to parent together, consistently. No more 'good cop, bad cop'. To her this is like being a chicken living in a coop with holes large enough to admit a fox. It frightens her to be able to manipulate her father the way he is letting her. She is not feeling secure.
For him:
No more hiding in the bathroom when she is violent.
No more begging you for an easy life. No more 'FGS give her the tablet'. He has to get a grip on his own anxiety here.
No more replacing of broken things with new.
He has to back you up immediately if DD attacks you.
What he is doing now is 'permissive parenting' bordering on 'neglectful parenting', that comes from denial, which comes fear and maybe a little laziness or a tendency to avoid problems instead of dealing with them. The result is misery and anxiety in your DD, with violence and chaos as her way of communicating that (and a younger child who is having a very hard time, I guarantee it).
She needs him to 'stand up' to her. He can do this by adopting an authoritative style of parenting and backing you up when you parent this way.
This is not authoritarian parenting, but authoritative parenting:
www.parentingforbrain.com/authoritative-parenting/
It is appropriate for children with a lot of anxiety.
You can follow the tenets of therapeutic parenting alongside this style, or integrate all the elements. Each style features emotional responsiveness and solid demands/expectations based on the emotional age of the child which are not let slide.
She feels connected and safe in school, and can function in at least one area thanks to the structured environment and clearly defined 'walls' (rules and consequences, expectations set forth clearly, predictable routine every day). The aim in authoritative parenting is to establish a predictable social and emotional environment in which a child can always know where she stands. The aim in therapeutic parenting is to foster feelings of connection to the family, and physical and emotional safety. You don't need reward charts, and you can forget about the chronological age as a guide to your behaviour expectations. Your guide for responsiveness should be the emotional age.
Therapeutic parenting is not just for foster children or children with an attachment disorder, or traumatised children.
www.selftimeout.org/assets/ther-parenting-tools.pdf
Long, sorry.
This approach focuses on the voluntary 'self time out' as an opportunity for reflection. You could have a safe place for her that has a weighted blanket she could get in under.
Therapeutic parenting involves creating a highly structured environment, and not just in terms of a timetable. If you choose this approach, you will need to plan for every eventuality and put your planned responses in place every time specific situations crop up.