I agree with Navy Mom: he should have gone home FIRST to talk with Claudette before he went to track down Todd. It seems that Claudette wasn't upset by the fact of his past with Nicola, when he finally did tell her -- it was only when, under pressure, he admitted the infidelity to Nicole. Maybe she wouldn't have pressed him so hard, , or maybe her reaction might not have been as extreme, if she hadn't just spent days wondering where he was and what he was up to, triggering her own fears of infidelity.
But Myrna's advice was wrong (though she could never have realized this wasn't what she imagined, reviving an old flame). It was essential for Daniel to deal with the unresolved question of his guilt in order to move on. That sense of guilt is exactly what made him afraid to talk to Claudette in the first place, long before he ever heard Nicola's voice on the radio... so his behavior here was consistent, not just a plot device. Despite the unhappiness that follows for the family, ultimately we are left with the sense that he is better for it, because he's overcome his demons (and the drugs he used to keep them at bay) and we see him beginning again with Claudette on an honest footing.