I too have fallen more when I had flat pedals than when I went clipless
I too have frogs, you said you had difficulty clipping out fast enough.
The guy at the LBS who sold them to me uses them too and told me to put a little chain wax/oil (I use white lightning on them) on both the cleats and the pedals and wipe it off. He said to do it about every week or so depending on how much you ride. I find they go in and out much smoother then
also are you just giving your heel a quick out twist for it to release?
When I have steep down with a turn at the bottom I always unclip 1 foot - for me it is always left out first and in last (I am left foot dominate) If ever I need to pedal a little my right foot can catch the brunt and I can still pedal w/ my left a little w/o clipping in.
I went around and around and around the bike path at the park until I was comfortable. I always make sure my one foot is in Ok and then get my left foot in (I have gone through a lot of intersections after a light pedalling w/ only my right foot
It's about the journey and being in the moment, not about the destination