Authorities found 73,755 child sex abuse images and video files on devices seized from his home in late 2015, the court had previously heard.
In June 2016, while he was on bail for the child pornography charges, he had used a phone with access to the internet - in breach of his bail conditions.
He had also joined as a volunteer at the iHeart Church near Queen Victoria Market - another breach of his conditions.
He did not tell the church about his sex offender registration or his pending charges.
The iHeart Church previously said Henderson had attended a youth camp with 32 children in April 2016.
In the County Court of Victoria on Thursday, Ms Skoblar said a psychologist considered Henderson to be at high risk of re-offending.
Defence barrister Camille Woodward said at the time of his offending, Henderson was extremely socially isolated.
She also said he had no malicious intent upon joining the iHeart Church and that he had largely complied with authorities since his arrest.
Also on Thursday, Henderson's defence team was knocked back in a request to gag media articles about having breached his registered sex offender conditions.
He is due to appear in court on June 6 for sentencing.