Nugget is pretty gimmicky, but it's interesting at the same time. Sure opening it (or pulling it from your prizes) SUCKS, on the flipside then they'll simply be discard fodder. One thing I'm intrigued about (ruling wise) is if you draw a Nugget from the effect of Nugget, I'm going to assume that if that happens, it sucks as well.
Depends. The translation you see here is not final, and it really depends on the translation. If I had to guess, you won't be able to use Nugget on the effect of Nugget.
It's an interesting card, and I think it might be used as a 1-2 of in decks that already use SSH Oranguru. It's easily one of the best cards to choose when using the Ability unless you're using Torkoal V or something. If you just need draw power in the moment, this is probably one of the best cards to select, unless you're going for something like Quick Ball, N, etc. Even if you get Marnie'd, Oranguru is most likely not Knocked Out, meaning you can just do it again. And either which way, getting Marnie'd means you draw into some stuff, which is awesome.
However, I think in general this card is bad. Mill is simply just going to erase it from your deck, making it not nearly as useful as you want it to be in those matchups. Chip Chip can also just stop the card from ever activating.