1) No, just use it on cooldown and macro Rabid into stuff.
2) BW does not improve Stampede btw. If AoC procs, you use Stampede no matter what.
3) Always use Kill Command on cooldown if it won't mean that Beast Cleave drops. Multi-Shot is awful, awful damage. Replace Arcane Shot with Multi at 4 targets.
4) Don't consume when 1) TED is up or 2) BW is up or 3) BW will come off cd in less than 10 seconds.
5) I don't, but it is a DPS increase, I just don't bother. (It's relatively low prio, and it's only worth it when ToTH is not up, e.g. Serpent Sting is half the cost of Arcane for more damage).
I has done the mathz.
Reasoning:
2) The damage loss of not overlapping as much Stampede/AoC uptime as possible is much, much greater than not getting another Arcane Shot. Casting Stampede is also free, so the DPF is much higher too.
3) At 4 targets, Multi-Shot DPET beats Arcane Shot, but you need like 10+ targets for Multi-Shot to beat Kill Command's DPE. With ToTH up, it costs half the focus of Kill Command which is valuable, but if you don't drop Beast Cleave by using Kill Command, use it.
4) Spending a non-damaging global during TED is bad. FF gets your pet a guaranteed 100%+ basic attack, but it can take up to 2.5 seconds for this to actually land, by which time you've already dropped 5 stacks, and the damage bonus here doesn't beat a single Arcane Shot to start with.
Same story with BW, unless the only alternative is literally Cobra Shot, you don't use FF when BW/TED is up.
The reason for a 10 second wait (many would argue that you miss out on a bunch of Wild Hunt uptime this way) is:
1) Uptime is so high anyway, regardless of FF or not.
2) 10 seconds allows for 3 basic attacks, which is 3x40% chance to build stacks again before you BW.
5) Serpent Sting does more damage than Arcane Shot for half the cost, it's a no-brainer to multidot with it, but if you mess it up, that DPS increase is gone.
Here's a helpful string for when to use Focus Fire, meeting all the conditions I listed above. I recommend removing it from your bars so you don't accidentally react to the shiny, and just reacting to when this comes up.
Code:
d4dpgaGAvuvRxuvonITbiAFIQQMjQQ5kqMnqxg6MsHUTu5BcW5LQ2PkSxYUv1(Ls9trvgMevJtG6VIYqfvgmanCbDqjYPevvogLY5qvSqkPLsjSyKQLd6HsONQ8yj55OSmkrtvKjJuMovxucUQeLNjGUofBKs1wbe2ms2UKAAQiFvfv5ZOY3LcgjQshwOrdOgVuYjLIUfG01aW9urzLQOIrPIk9BvAztjnIwZ3rivScdQz19zb18aiYAKWQYA8(mhHfbJnKvEGAmnyGaO1PrtJMsA0iSZ38voPgfDTkdZVDjSLRrDRmS2asrGy7ZrRppkkg6YoqdoaGeGYpfmp8ema8yja2Suua9uaAoKWXHqL0Qmm)2LbmHgQ5KoKMM5XA8DTOXVAyn(UwrGJEBaBezSihQvDnVNxicJ(fQD2zAMN4AHORzyyXR5DzvR6AExdani2PbGge7YleHr)c1o7mTp2HmL0Hnn7q8ZxVCnddZmpXLv5Au331kawxwZ2aA)(Ug4nstjnddZQaJmMSQbVGOsADgqNOKC5AvGrgtjng55arnEl7ivWc5Y1Gih5(P(quJuDFTQ7fK2THxw1Ig)k6AeAALY3fA3U1R5RqTinAeNC)iyMdjCCiKPKoSPKMdjCCiujnVpe1yE0nmnZJ147ArJF1GyxK8KNl7gIWOFHA5)zAyn(UwX7fK2THVnG5GxoiYyTb8CxiccMFAmdDSgFphePiT0wUc85RzyyglebbpIDOSQbXUi5jpNMnBAggMbXUi5jpNSQzEIRfcg7rOMHHzMN4YQgZqhRX3NHII0slRyPLYwQKfjnwiccEe7qDyJhac4KCnZ7qchhcvsJfIGGhXouh24bGaojxUoSujnhs44qOsA0q6gkQuFiQXBb(5SxgFnVpe1IgyuJ81iKHYQgZqhRX3NHII0slRyPLYwQKfjnZtCTqWypc1(yhYush20saJTb0kgzEBappIdm5LRH147A8IrqhynMHowJVNdIuKwAlxb(8LRzEhs44qOsYLRJavsZHeooeQKgZqhRX3ZbrkslTLRaF(AEFiQfnWOg5RridLvnMHowJVpdffPLwwXslLTujlsAMN4AHGXEeQ9XoKPKoSPzbYCqKXAdyjociX7LRH147A8IrqhynAiDdfvQpe14Ta)C2lJVCnZ7qchhcvsUCDCsjnhs44qOsAEFiQfnWOgZqhRX3NHII0slRyPLYwQKfjTBdFEpyVSQH147A8IrqhynMHowJVNdIuKwAlxb(81iFnczOSQ9XoKPKoSPz)wzyTb0obIY1mpX1cbJ9iuJgs3qrL6drnElWpN9Y4lxZ8oKWXHqLKlxUwR8OOyOl7anaEozPLNoXtGbgSLbdKLhSOa6Pa0Etxcs44qithaOfFsx0j3xjTUi5vsZ7drTqiYqxleIm01OFnFfkxUgnclem23S6(AnpsfSWEPIfcQzX8owqr6eqI3NbS5DeMrDRmmkceLRfvsZoe)81R18DesfRWGAwDFwqnpaISgjSQSgVpZryrWydzLhOCTADy7KTYLlb