He didn't have full control over Ludo. He could give suggestions, but not take full possession of him except for explicit instances where high levels of magic were being released.
1) First possess Ludo when Eclipsa's chapter is opened, and does nothing else but talk to Glossaryck and tell him to hide;
2) Absorbs Moon's magic, defeats the High Commission, and loses possession. Ludo wakes up the next morning with no memory;
3) Glossaryck's book burns, he gets to possess him for half a minute to talk to the dying god;
4) Possesses Ludo one final time to force Moon to give back his finger.
Making sure Eclipsa was alive was irrelevant to what he was doing. He had to complete several tasks in a short amount of time, and he had to rely on someone with Ludo's physique to intimidate and strongarm those plans to fruition. Toffee never had time to verify anything, and even if he wanted to, Ludo being a monster would set off so many magical alarms he wouldn't find out the truth anyways.