1) If you don't have the Riven just put [Vicious Frost].
2) I have [Primed Reach] on for arbitration drones and now I need the range lmao. If you wanna replace that you can use either a heat mod or [Sacrificial Steel]. [Sacrificial Steel] gets you to 128.5k damage per second. Heat however, is better for high armored enemies (50% armor strip).
3) I use the [Brutal Tide] stance for it's mobility. Also last time I checked, the other stance had too many forced impact procs on the block combo which I am not a fan of.