Actually no, he was starting to act more calmly. Tam jumping off script made it super-dramatic, but it was working before that--and in a much safer manner.
She didn't see Tam would jump off script. That was a mistake on her part. But the plan was working, and did work.
That's an inarguable point and I'm not sure why you would make it, the shock of how it did play out to Rand is the catalyst in the story, and there is nothing that supports the idea that another 5 minutes of script reading would've resulted in any more than a bandaid for a few days.
Also I simply cannot see how RJ would have written this entire series if one of the most important and personal events came down to Rand's father bs'ing with someone elses script. Too contrived and cynical.