1.) Bouncing fish doesn't have any real 'kill' setups outside of at the end of f-airplanes or an offstage airdodge read.
2.) BF usually will kill you off the side, so up and in would be optimal there. However, if you're near the ceiling, then down and away would be best to avoid ding off the top.
3.) Shield would probably always be your best option, but try and do it on reaction rather than anticipation or you may get grabbed. If airborne, some aerials may beat it, or you could airdodge. I feel like a double jump+airdodge would be best, assuming the BF isn't a true combo from something. And as always, what you do can be read and used against you.