Hi,
1) If a product's best before date is June 4 and we are on June 9, do you say the product is "due"? No. I say It's past its "best by" date or perhaps just It's stale.
2) Can you speak about a weighty person? Yes. But if you are talking about physical weight, more common would be 'a heavy person'.
3) Can you speak about a thriving person / product? For a person or a living entity like a plant, yes. But for things, I think it depends on the particular thing and perhaps the context. For people-related things, it sounds OK, eg a thriving store. But it sounds wrong to say a thriving book. A thriving product also sounds odd to me.
Best wishes, Clive