Keep the straps loose. There's really no reason to cinch your foot into place. Toe clips (and clipless) take some getting used to, but really are great once you get the hang of it.
Go ahead and start out on the flat side of the pedal. Practice flipping the pedal around when you've got your balance and then slip into the clips.
Get out of the clips early when you're coming up on a stop. Practice getting out with either foot first and get both feet out earlier than you think you have to. Be safe and don't worry about speed.
Knock on wood, I've never had a fall. Came close this summer when I switched to clipless and it was a dreadful, helpless feeling.
BTW, great to hear you're just getting back into biking! Good luck with the plantar fasciitis. I had a bout with it a few years back which I eventually traced to my shoes. They were those slip-on funky-looking backless jobs. As soon as I got rid of them my problems went away. Very painful while healing, though.