Volume issues integrating with logic and youtube

Hi, I make alot of music videos where i record into logic then sending the mix to final cut pro x and add the video before uploading to youtube.

I've been doing this for a few months and i find that many/most of the videos i upload have volume issues. My track will sound clear and loud enough when i record in logic, and it will sound clear and loud enough on my imac when editing in final cut pro x, but when I upload the track to youtube and watch it there- it is often very quiet (difficult to hear the speech/singing/playing) and sometimes gets heavily distorted.

(An example of the distortion can be heard at 35 seconds into this video:
)

I have noticed that the distortion usually seems to be a result of raising the volume in final cut pro x. To counteract the low volume that i expect the youtube video will have, I have usually been raising the volume by 12dB on the audio clip in the final cut pro x timeline. When i raise it a bit less (like 6dB), the distortion tends to decrease and, when i raise it by more, the distortion gets very bad . Is it ever useful to raise the volume in final cut pro x like this, or does it distort audio for everything? Or maybe i’m just doing it wrong?

I’ve tried raising the volume in logic too, but i’m not sure what i should do. The audio has been recorded a pretty high quality microphone (aston origin) at 6 to 9/10 volume on my audio interface (scarlett 18i20 by focusrite) and many of the midi instruments already have gain plug-ins to increase their volume. I usually leave all other volume settings at their default.


I'm wondering if there is a better process/workflow/steps to take that can fix these issues and make for videos with louder audio. Maybe there are other volume settings or bounce settings in logic that i should be doing differently than i currently am (i’m currently bouncing by either sending to media browser or sending to iTunes then dropping it into the final cut pro x browser). Or maybe there is a better way to raise the volume in final cut pro x without causing distorting?

Or maybe other settings in the youtube upload? Maybe youtube is compressing the video or something like that which is causing the problems?

Are these types of volume issues common? And what is the best way to fix them so that they don’t happen anymore?

Also:
In addition to my lack of knowledge about better ways to raise the volume, it’s also been tricky to set the volume at an appropriate level that people watching on smart phones and devices with small speakers can hear it relatively well (when i am monitoring on the bigger iMac speakers or professional headphones). Does anybody have any experience with this and input to offer about it?

Thanks, Dan

UPDATE:

I just noticed that the distortions often come at parts in the final cut pro x timeline where the audio wave form goes into the yellow and red. However, the audio file sounds fine on my computer, there's never any distortion when it's in the red. What accounts for this?


I also just googled "low volume upload youtube" and found that alot of people had written about this kind of issue, but i didn't see any definitive answers that seemed to fix the issue. A couple people mentioned checking my audio encoder and some mentioned normalizing the audio in the editing program.

I'm unfamiliar with both of these terms/processes and not sure if they will fix the issues. Anybody have any input on this information?