120, we already do that I'm afraid. We make sure he is ready at least 20 minutes before we need to leave and then he sits and reads a book until its time to go. He is usually fine with actually leaving the house, its unstructured time he doesn't cope with.
Thinking back, there were lots of extra things to remember this morning (both boys had two letters and money to hand in, its viola lesson day for ds1 and ds2 needed to remember he is having a special school dinner, plus there were lots of extra bags of stuff that needed taking in to organise) so I think there was a slight lag in getting stuff together and getting out the door, which gave him time to get distracted.
Morning meltdowns are usually related to him wanting to do some unsuitable/lengthy game or activity before school and not liking being told no. So fairly typical 8 year old boy behaviour but a bit more complicated, rather than ASD stuff.
Books, sorry you had a crappy start to the day as well. Hope you have managed to recover now.
With the sofa sitting thing. In clicker training, you would start with a reward (so a book or favourite toy is perfect) and every time she sits nicely you would give her the book/toy. Then eventually, when you are getting a consistent correct response, you would start dropping the book from the process intermittently, maybe a book 4/5 times then 3/5 then 2/5 then go to only giving her a book completely randomly. By rights, if you were clicker training, you wouldn't say "would you like a book?" you would just give her the book as a reward every time she sat down so that she started to pair the action with the reward. Also, in theory, being told they are 'a good girl' is pretty rewarding to little ones in itself, so - again in theory - as long as its a strong enough motivator to please Mummy and get a 'good girl' strictly speaking the book shouldn't be necessary. That said, personally I think the book is still a great idea, as it will teach her to stay sitting, rather than getting up straight away.
Did any of that make sense? I know what I'm doing with operant conditioning, but find it hard to explain it to people without going into too much detail, getting to wordy and making it sound far more complicated than it actually is. (You know me, always 10 word when 1 will do ) Its really such a simple concept, its brilliant in its simplicity.
Oh and at forward roll - my two boys still can't do one of those!