4 newb torpedo questions

I'm in the Academy now.

1) How do I find out how many torps I got left whilst submerged or in the ship?
2) Can I move aft torpedoes to the front?
3) What is the speed button (s/mf/)? I suppose it increases the speed of the torpedo, but what are the consequences? Might as well set it to "fast", but I suppose there's specific reasons to do (or not to do) so.
4) What is the M/I setting for Torpedoes? My guess is "Impact/Magnetic". Impact must be precise, but Magnetic...near? When to use which?
5) What are reasonable max ranges to engage at?

I'm using the LSH 3 mod in case it's relevant (what do I know).

~ Cheers!