So when Dumbledore was disarmed as the Elder Wand owner he “lost” its loyalty to Draco. In the Deathly Hallows, Harry disarms Draco in the Malfoy Manner during their (Harry and gang's) escape from the mansion.

Did Harry get in trouble for using Sectumsempra on Draco?

Snape saved Draco, and having realised that Harry got a hold of the old textbook, he punished Harry with a multitude of detentions for nearly killing Malfoy. Harry, despite disliking Malfoy, did not truly want to harm Malfoy to such an extent, and was both horrified and guilt-ridden by using the curse against him.

Does Harry save Draco?

A disinclined Death Eater

By refusing, Draco finally took a stand and stopped another innocent person being brutalised. Actions have consequences – Draco learnt that the hard way. Harry would later risk his own life to save Draco from the Fiendfyre.