1. 1-2x OP is all you'll need before you start HS -> SSing. Fracture is actually really good at low level, so what I tended to do was (OP x2) -> (HS -> SS main target) -> (Fracture second target) -> (HS -> SS main target) -> (Fracture third target if there is one) -> etc. Later on Fracture will be next to worthless, but for now it'll be really helpful to keep hate.

2. Once you have access to Butcher's Block you'll have much more wiggle room to keep your Maim buff up. After enough HS -> SSs you can take the short risk of applying Maim, which will give you more enmity for the SS combos you do while it's up. As long as the mob isn't about to go and rip open your DPS/healers face then it's safe to go for Maim as it'll be helpful in the long run. When you have access to Vengeance and/or Berserk, you'll have a lot of time to apply the SP debuff to the other mobs. If you're worried you can do HS -> Maim on your main target, and then tab to the other target and SP. Any damage generates enmity so applying Maim also gives some enmity, which is why it's usually not a risk to go for it.