Get some SPD pedals, for example, Shimano PD-M520. As for the second question, it is easy to unclip, the problem is that it takes some time for this to became a reflex. What this means in practice is that you may be doing great with conscious unclipping, you'll start feeling confident, you'll not fall... until one day you'll need to do a hard emergency stop, you'll forget about everything else, you'll stop and fall. Good thing is that the fall will accelerate development of the unclipping reflex.

For me SPD pedals and proper cycling shoes made a huge difference, it felt as if I got a pair of wings attached. Safety is an interesting question. On one hand, I did fall several times because forgot (or was not fast enough) to unclip. However, all of these falls were at zero speed, so very little harm done. On the other hand, these pedals already saved me a few times during high speed emergency avoidance maneuvers and unexpected jumps over obstacles. Without them I'd for sure as a bare minimum would have been hit by pedals once one of my leg lost contact (and other kept rotating crank) and/or went down hard - being clipped allowed to pull the bicycle and avoid crash.