Totally understandable concerns. Wearing a helmet and carrying your phone and id should help with #1. As for #2...well, you are on a bike, so hopefully you could get away from someone if you had too
Maybe just start on well used paths, avoid going at off hours, see if there are any groups that ride in your area, or perhaps stick to riding around your neighborhood for a while if it is rideable.
There is a path near me that is pretty busy at the trail head with walkers/runners, but by mile 2-3 it is pretty quiet. I do get a bit nervous riding it by myself, but ultimately I am not going to let it stop me.
Also, always let someone know when/where you are riding if you are going to be out alone.