3) Usually the reason the A/V are out of sync is related to the frame rate (i.e. the -r parameter on the ffmpeg command).
Try a variety of frame rates and OpenShot project types to find one that doesn't have A/V sync issues. Some common rates are: -r 29.97 -r 25 -r 30 -r 60
Try a variety of frame rates and OpenShot project types to find one that doesn't have A/V sync issues.