1) See point below #3
2) If you suspect you'll be recorded, don't play it (only MOST music from XIV's OST is technically allowed, even songs from other FF titles are disallowed)
3) Same as 2

SE's TOS clearly states that we're strictly forbidden from uploading Perform recordings of songs that aren't from XIV (themes by Uematsu also being part of that ban). But generally speaking, judging by the way SE has handled similarly difficult to judge questions about actions technically running afoul of the TOS in the past (most notably parsing)... if you don't draw attention to yourself by sharing things they tell you not to record, they won't police you for playing a tune they don't own for a crowd in-game. Basically "don't force our hands by being an obvious ass about it". But since you never know who's recording/streaming what, you might want to limit your audience just to people you trust if you want to play something outside of XIV's OST.