Sorry! This new phone does whatever it wants to!! Ok- skip adding more ammonia after it has zeroed & do a 90-100% water change with temperature matched, properly conditioned water. It may take more than one big water change to drop your nitrates down to your tap level. Make sure the new tanks water matches temp of his tank water. No nets to move him- use an open-mouthed pitcher full of his water. Let the new tank run for hr before moving him.
Then, I would start dosing the small tank daily with ammonia to keep it cycled in the event he needs to be moved back for other treatment beyond the med food- or keep him in the small tank until he is completely healed up & continue to dose the big tank until he is ready for the move. I hope this makes sense!! If I confused you, just let me know!