That's such good news about his spleen tumour being benign. My Brogan died of a cancerous spleen tumour (splenic tumour?) so I've really been holding my breath for you. I wonder if they prioritised the spleen and not the gland for the first surgery because of the danger of the tumour? I have a very limited understanding, but remember from Brogan that if a cancerous splenic tumour bursts, it's death within hours, nothing they can do. So maybe that was the priority, get that out safely in case it was cancerous (thank goodness it wasn't) and then focus on the gland issue.
I know the idea of another surgery so soon is really scary/exhausting and I don't understand the medical side of it, but as
@Jacqui-S says 'better out than in' and maybe it will be such a relief for you if he's not having the dangerous effects it's creating.