Your kickr transmits power in both BTLE and ANT+ (not speed)
Your iPad can pair to your kickr with bluetooth, but will not "see" any ANT+ sensors.

That is *all* you need to use zwift. Anything else is maybe nice to have or even desirable but not necessary. Your garmin head unit is completely unnecessary. A Heart rate monitor is nice to have and cadence is nice to have.

I gave up on Garmin sensors a couple years ago because their mule-headedness about making them ANT+ only limits me. Those things tend to wear out after a few years anyway, so next time you need one, just get a BT / ANT sensor. Wahoo makes some nice sensors.

I got my wife that CABLE device so she can use her garmin footpod and jog on her treadmill. It does a nice job, so if you want that so you can use your ANT+ sensors with your iPad, it'll work well for you.