[subject] + 尚 + [adjective] / [verb]
[A] + 尚且 + [predicate],(更 / 何况) + [B]
尚 is the written "still". It goes right before a verb or a one-syllable adjective and says a state hasn't ended yet. Speech uses 还 for the same job.
尚 mostly pairs with one-syllable words, and the pairs read as fixed units: 尚早, 尚在, 尚存, 尚无, 尚有. Before a longer predicate, writing uses 仍 or 仍然.
尚可 is a mild verdict – acceptable, but nothing more. It turns up in reviews, reports and marking.
尚且 marks the case where the result is least expected: even A is like this, so B certainly is. The second clause starts with 何况 or carries 更.
尚且 has to sit on the less likely case. Put it on the obvious one and the logic runs backwards.
尚未 is the negative, "not yet", and is covered with 未. 问题尚存 says the problem still exists; 问题尚未解决 says it hasn't been solved yet.
尚 doesn't fit chat.