props for getting out and learning man.
A left facing stop doesn't always need your back foot to scrape as well. It will come with time, but your right foot should be dominant during this stop anyways. I taught a few friends stops/starts a couple weeks ago at public skating. I found it was easier for them to stop with one foot (right foot) and just leave the left foot a bit in the air, after the stop is completed, the left foot can be dropped, and then a single right foot crossover can be done go get some speed into the opposite direction
Backwards crossovers stay low and put an arm in the air for balance. the lower your centre of gravity is and the wider your stance, the easier it will be.
The first time learning to stop using your weaker side is a lot tougher than learning with your strong side. Just slowly work your way into a full stop. Angle your foot just a little bit more each time. Even if your not stopping but just slowing yourself down, it will help you become more comfortable using your left foot. This is also hard to learn because you will be on the wrong edge of your right skate. Pratice your crossovers turning right first and this stop will come soon after.