Hi, I've moved this thread to Help, Tips & Tricks where it seems to fit better.
Also, popping reply in spoiler tags, though I don't think it's all that spoilery ...
I believe you can refuse to help him, or just not give him stuff if you don't want to. He'll probably get sniffy, but if you'd rather keep your magic items, many of which aren't all that useful to many classes and don't fetch all that much gold, than help him then presumably you're okay with that!
But he also shouldn't need all that much, and especially in the full release as he can consume almost any magic item it shouldn't be hard to find things you don't really need. In my playthrough, I think it was after three items he said they weren't helping any more. How many items have you given him, and are you getting the message that they're no longer stabilising his condition?
