Clipless pedals are actually very safe because your natural "panic" reaction of putting your foot down is what unclips you. The only time this does not happen is when the rider's brain decides to overthink it and overrides it and they don't unclip. So basically go to a field and try to fall over with your brain shut off.
As for hills and stops, learn to modulate your speed with little touches of the brakes and stop grabbing the levers. You can read online about countersteering, but it's best to learn from someone else. The basic idea is that you lean the bike over into a turn so that the wheel turns in the opposite direction and changes your direction in a hurry. Hard to picture, but it works and helps when you need to make a fast turn or get around something in your way.
I'd suggest you do some group rides where you can ride in the safety of a pack and learn from other people. Austin Flyers Women's cycling has group rides and who knows, you might end up wanting to join them
http://www.austinflyerswomenscycling.com/our_events.php