1.my bottom leaves get limp and droop and die

Usually caused by overwatering or soggy soil.

.What is the best way to propagate them? I tried sticking a leaf in some
potting soil after dipping it in rooting powder and it took, but then it got a
white powdery look to it and doesn't look too good.

Do not use rooting powder. You want to encourage sprouting first, then rooting
later. Make a clean slanted cut on the petiole and plant it in Perlite or a
soilless rooting mix. Then put a baggie over it. Keep it moist, but not wet.

Iris,
Central NY, Zone 5a, Sunset Zone 40
"If we see light at the end of the tunnel, It's the light of the oncoming
train."
Robert Lowell (1917-1977)