things sound rough at home.
From my bad days with my boys, I would say that there are some overlaps, but if there's an increase in meltdowns, there is probably more than meet the eye. Their emotional fragility depend on their sense of well-being - e.g. on a normal day, they will just ask me to cut the tag off for them with p's and q's. On a bad day it would be whining and crying and finally, (accusatory)"why didn't you cut it off?! You know I don't like it! You know that!!" More wailing.
It could be something as simple as being tired and hungry, being over scheduled and hence burnt out, or something could be going on in school that's bothering ds1; for ds2 it would be when his eczema is flaring up. During these episodes, unreasonable as they seem, the best response is TLC, snacks, and staying calm.
You did not say much about your daughter, but we've been to the OT who recommended me The Out Of Sync Child for reading. The head OT did tell me that in his experience there are some overlaps in the profile between children with SPD and gifted kids that go to him, so it's pretty hard to tease them apart, but generally, when the child is more comfortable and confident of his body, he will be more accomodating towards the outside world. I see that in DS1. His improved agility and reaction time mean that he's no longer on the defensive around other kids, because physically, he can handle or anticipate them now.
As for the being sensitive to facial expressions, yeah, that's DS1 too. The psychologist even noted that in her report. I dealt with that head on. I had a talk with DS1 and told him not to read too deeply into things. We talked about other people having bad days and how that affects their behaviour, it could be a passing thought etc. We have an agreement that if he's ever not sure what my expression or tone mean, he is to ASK me, and he has done so many times since that talk. I wouldn't have believed that I had to spell it out for him, but I did.
By the way, did you previously post on your daughter's reading and I put a link to visual-spatial learning? I just want to add that another mum later mentioned a book Reading Reflex and I checked it out of the library and have been trying it out with DS1 and I'm seeing improvement! (thanks to that mum!) His spelling has taken a great leap forward and he can now spell things that he couldn't just three weeks ago.
I also read up on the Ron Davis method and the idea of "trigger words" - certain words that the brain stumble over and confuses the child while reading. I got DS1 to read me two pages, noting down all the words he stumbled over - words that I would have expected him to know - and it has been quite a revelation to me. He had a small number of sight words confused, or had them identified as another anagram. Because they occur so frequently, his reading was halting, but once these words were removed, he was much more fluent. We are now working on re-learning these words thoroughly to re-wire the eye-brain connection. (Ron Davis method apparently involves moulding clay words, but I think you can find your own method.) His reading confidence has soared now that he understands what is going on.
His left-right orientation is still confused, so we still rely a lot on strategies for reading and writing orientation, but it's still one of the biggest improvement I've seen in the past year.
hope something in the above ramble is useful.
And if you were not the same poster who had raised the reading issue, I really apologise for being irrelevant!