Gift ideas

An 'iou' from you for anything he particularly likes (within reason ) say for a special meal, or a a trip somewhere, even a day of silence

That’s a good idea for a meal of his choice. He regularly gets silence. It can be for days at a time   .

I’m going to make a mini scroll to write it on. The plan is currently forming.

Are you any good at calligraphy,  that's another skill I respect but don't have.

100% not in the slightest. But wish I could do the arty writing

There's always the printer, but doing a miniature scroll might be tricky. You could distress the paper and dye it with tea before printing.