1. Yes, always sim yourself for proper weights and upgrades.
2. Take SimC dps with a grain of salt. It assumes full buffs, patchwerk fights and perfect gameplay. As for the rotation, depends on if you have the Dreamcatcher legendary or not. If you don't have it, the rotation is simply is to keep up dots, keep New Moon charges rolling, use empowerments and spend resources on starsurge. Avoid capping on AP or wasting empowerment stacks. To minmax, you can cast starsurge/moonfire/sunfire more wisely (e.g. when you have a CD or trinket buff up) but don't go out of your way to do this or you'll likely
lose dps.
3. You'll need to sim yourself. 30-33% haste is only really necessary with the Dreamcatcher. For example, I don't have it yet (grr) and haste is valued less for me. I have barely 24% haste.
4. Kind of depends on what you have and your current stat weights, I'm honestly not sure if there is an ideal setup. Get any pieces you can and sim away. I would imagine the 3 best will always be the haste pieces, then whatever other piece has stats you desire.
5. Probably, but kiss Gebuz and Tunderer for this gem:
clicky
6. In general yup.