Diablo 1 HD Hellfire Mod | Awake

In normal difficulty, the sell limit was 50000; anything more would default to 50k.

I would've thought that cap would increase in the following difficulties, but in Nightmare, I still can't sell a few things I have that are worth more than 50000, for any higher.
(Good rare rings/amulets often sell for a ton)

Is there a way to ever sell for more than 50000? And if not, would it be possible to add it in?

I think you should salvage all/most of your items, there is more than enough gold from gold drops alone..

All mag items should be salvaged for crafting after Anvil of Fury.
Normal difficulty crafted items are generally useless except to make low level rings to salvage for silver oil.
Nightmare crafted items are generally weak unless you get very lucky.