Hi Kev,
I listened to both of your videos of "How Did You Know". I only listened to the live performance one first, but I could barely hear your singing in it, so I listened to the earlier one that you did under, probably, more controlled circumstances.
For the performance, the only thing I can think of is to try to connect with your audience more. Now, I don't know how you introduced your song or what you did after you were done singing, so I can only go by the song itself. It looks like you do the same thing I do--shut your eyes a lot. I have to try hard to remember to keep my eyes open and look around at the audience. I also always forget to smile, at least a little. And I try to remember to put some expression on my face, something to make it look like I'm expressing whatever's going on in the song.
You mentioned being aware you had issues with your voice. I noticed what sounded like missed pitches? Your vocal quality sounds fine to me, and I think some drilling on your own--and maybe taking advantage of some vocal coaching, if you're able to do so--would help a lot with getting more accurate with matching pitches. I don't think it would take much, really. If you have Melodyne, or something similar, you could record a song and then go through the recording in the software. It'll show you where your voice falls relative to where the pitch should be. Getting a visual like that can help improve pitch.
One thing to remember about performing. Most people listening will think what you're doing sounds better than you think it does. I've noticed I'm far more critical than most people, in general, especially about my own performing. You're probably the same way.
I really like your guitar playing, by the way. I forgot to mention that earlier.
I hope this is a little bit helpful??
Vicki