How can I help my 6y/o daughter?

Hi everyone,

I'm new and I apologise for the long post but hoping someone can maybe help or give some advice.  

My youngest daughter seems to show classic signs of being on the autistic spectrum.  At present, I am not looking for her to be formally diagnosed as I believe her to be high functioning and hopefully we can help her without a formal label.  This may change if her coping ability changes etc.

She manages very well in her school environment, described as a bright, fun, friendly child who listens and leads others in group activities etc. 

At home she is a different story. 

We were experiencing multiple tantrums on a daily basis which were becoming violent (only towards me, never towards her sister or father...in fact she rarely threw a tantrum when grandparents were looking after her either). 

I spoke to school early this year to ask how she was managing and explained the situation at home and school have been helping with some emotional literacy sessions which has made a massive improvement to her general behaviour and she has not had a violent outburst at me for nearly 10 months which is amazing! 

She has always had some issues with the way her clothes feel, refuses to wear jeans because they 'feel too hard', will not entertain jogging bottoms because they 'feel too flappy', trainers and shoes are often too tight (even though they aren't physically too tight) and socks with patterns are 'too bumpy' etc etc but generally we have managed to distract, bargain, discuss, alter and provide alternatives so its been manageable. 

What I am finding is that since we have seen an improvement in her general tantrum behaviour, her clothing issues are becoming more frequent (every single day) and more extreme.  Clothing that has previously been acceptable to her is now off limits.  My usual techniques (distraction, bargaining etc as above) are no longer cutting the mustard and she has meltdowns every single morning about her school uniform which is not something that I can change...I cant simply put her in something else so these episodes are beginning to take a massive toll on her and my husband and I, every morning is a battle and that battle is played on repeat every. single. day.

Does anyone have any advice on how I can approach these feelings?  We have tried talking to her, we have tried mindfulness techniques, I try to ensure she is well rested (don't get me started on the duvet issue!), I've tried calm, reasoning, bargaining, explained resilience, asked her what the specific problem is, let her choose from her selection of uniform each day, including pants and socks, tried to distract her with something else when getting dressed, praising her, and sadly scolding her...nothing helps and I am out of ideas.