You are following John's lead as far as allowing him to continue to nurse as long as he has interest, and he is starting to lose some interest.
I think the same type of guidance can be used for pumping for Jordan.
In addition to his medical issues, how does he feel about the breastmilk bottles he receives? Is he attached to them? Indifferent?
You could pump and freeze. THis would lose some of the immediate immune benefits but would still be a gentle source of nutrition for surgery recovery. (of course that will only keep for about 6 months in the freezer)
You could cut down to pumping one time a day just to keep a minimal milk supply in case he needs it later.