I think you’re 100% on the money with your summary.AL's reaction in the book still seems odd to me. The questions DV put to him were not hinting at Suzy's potential 'other life' but rather about the last time he saw Suzy, the weekend before she disappeared.
Now this might still be an upsetting memory for AL to remember, and rightly so. However, he did agree to be interviewed by DV and he must have known that potentially there was going to be some awkward or upsetting questions he would face.
If he felt this way (which his reaction to the questions seems to show), why put himself through it and agree to be interviewed in the first place? What sort of questions did he think DV would ask him?
This is JMOO of course but I do wonder if the following happened that weekend.
In an old documentary AL said the Friday night at Mossop's and then at the pub round the corner (presumably the Prince of Wales) had been a pleasant night out.
However, I do wonder if this actually was the case. As we know when AL was on holiday Suzy had apparently got herself a new boyfriend, so on this Friday night out did she tell him about this new man in her life, and the evening did not go as well as AL had said - maybe they had a disagreement and that's why they didn't go to the pub?
On the Saturday evening Suzy went to a party but AL wasn't invited (maybe because the new BF was there?), and on the Sunday Suzy went with her friends to Worthing that afternoon. AL did turn up but had to make his own way there and back. So that Saturday and Sunday it doesn't appear that Suzy wanted to be in AL's company much at all.
There was supposed to be a phone call that night around 10.15, but AL said he couldn't remember if Suzy called him or he had called her. It was supposedly about meeting up with friends on Tuesday night, but how do we know this for sure? Suzy wasn't around to tell the story, so for all we know it could have been AL getting angry with her for snubbing him that weekend.
So did DV's interview with him bring this all back, that maybe things were not so fine-and-dandy between him and Suzy after all? Hence his reaction by storming out of the meeting with DV and Caroline.
Even after all this time some things remain in the memory banks and hurt when a seemingly simple question is asked.