Hi, LL74.
I don't know if I can be much help, but wanted you to know that you are not alone.
I have similar problems with my dds. DD1 (7) is going through a dx for ASD. DD2 is 3.10.
DD1 has a thing about shoes getting dirty and yesterday she totally freaked because dd2 ran across the wet grass. She wanted me to bring her indoors and clean the shoes straight away. I felt torn, because dd2 was having a lovely time. DD1 started shouting at dd2 and it escalated until I told at dd2 to come inside .
We also had an incident where they where given free WALL-E masks after seeing the film at the local cinema. The masks were on a large poster and needed to be cut out.dd1 likes everything to stay 'as new' and started having a tantrum when dd2 said she was going to cut the mask out when we got home. In this case, I felt that it was just too unfair on dd2 and I let her cut out the mask. DH had to take dd1 out of the room, though and she was really upset about it.
Also,dd1 has a 'unique' way of watching DVDs. She only watches certain parts and uses the remote to skip large chunks of the film. DD2 gets upset, because naturally she wants to watch the whole thing. Usually, I let dd2 watch the whole film after pre-school, when dd1 isn't around. This isn't working ATM though, with the holidays, so I have had to occupy dd2 while dd1 watches the film.
I don't know how to handle these situations, TBH, and am just muddling through.
I think if you are working at changing routines,then you are doing what you can.
I imagine that it's a long process, but will be worth it.
How old is your ds? My dd has gradually become more flexible in some areas. Up until a year ago, I couldn't let dd2 wear a dress if dd1 wasn't wearing one but that doesn't bother her so much now.
Good luck, wish I had more advice for you