Yes you could increase the chicken wings to every other day without causing a problem. I know of others who've had success by adding something like bran or all-bran to each meal.
Has your vet ever commented on the reason for Fenby's problem? I ask because William, who's almost 9 years old, has had anal gland problems all his life and various vets have told me that it's because his anal glands are in the wrong place

. Vets have described their positioning as too high, too far in and floating. What it means is that regardless of his diet (used to be kibble, now raw) whatever is passing through doesn't help to empty the glands so they fill up and need emptying regularly. So I'm wondering if Fenby has the same problem?
So far William's never had an infection thank goodness. I don't know if that's just luck or if it has anything to do with the fact that they're always emptied by a vet, so the emptying is done by an internal method not external, which I believe is what many groomers and owners do. I try to leave them as long as possible between times and feeding raw has helped a bit, but they still have to emptied about every 3 to 4 months.