Arsenal, with two games to spare, could secure a place in the last 32 of the competition with victory in the return fixture in Norway on 26 November.
Arteta has now seen his side win three successive games in all competitions since they were undone by Leicester’s counter-attack last month.
Despite falling behind, Arsenal were able to brush aside their opponents without the need to bring on Pierre-Emerick Aubameyang, Alexandre Lacazette or Thomas Partey.
Arteta was all smiles at the end, fist-bumping Willock on the pitch after the full-time whistle, the 21-year-old pushing his claims for a first Premier League start of the season with a performance full of hunger and desire.
“The way he is approaching every opportunity shows how mature he is,” said Arteta when asked about Willock’s contribution.
“I’m impressed with the way he is communicating as well. I think he is developing the right way, he is a player I really like.
“He has some very special qualities and he deserves every minute that he’s playing and he’s showing it with performances, with goals and his attitude.”
The Gunners had fallen behind after failing to close down Ellingsen, whose excellent strike had Molde dreaming of one of the greatest results in their history.
It was the wake-up call the hosts needed, Arteta’s side playing with a higher intensity after equalising.
Arsenal’s future looks in good hands, Nketiah also impressing with his speed and work-rate while substitute Saka played a highly-intelligent pass to pick out Pepe for his goal.