#1
Hello everyone. I'd just like to know if anyone can critique/give me some advice with my voice. This is the first time I'm actually trying to sing while playing.

https://www.youtube.com/watch?v=k-zFB0B2Rvk&feature=youtu.be
#3
I've been singing back up vocals for my Metallica cover band for almost a year or so now. Nothing really spectacular. I've sang along to songs since I was young, but I haven't actually sang on my own like that. I've tried to in the past, but I've always been self conscious in my room when my family's home, so I hardly ever practice at all.
#4
Okay man.
I would recommend maybe getting a vocal coach, or getting a copy of the program;
Singing Success. I use that my self, and I've come a long way ever since. You can also just go on YouTube, and look for various warm-ups, scales, how to sing from diaphragm and so on...
But stick to Polly. Keep on practicing it. Maybe even without guitar in the beginning, so you don't have to think so much. (Breathing, guitar, singing)
And I know the feeling about being self conscious when your family is home. I was in the beginning to. Just tell them man? I'm sure they don't mind. Some of the exercises might sound slightly weird, and they might smile or laugh, but that is all there is to it man. Just tell them you want to learn to sing. And... You shouldn't even have to do the exercises as loud as you would be, when you are singing. Just do them quietly, but even to produce tone. It strengthens up your mid-range A LOT, and your voice won't feel as "tired" when going to sing.
About the guitar. You could perhaps tune it down, a half or a full step, so you can hit the notes easier. You might even prefer the tone of one of those tunings.

But keep at it my friend.
#5
I need to work on my vocals as well. Not an expert, but playing the melody of a song and humming with the acoustic against your body, getting in tune with the melody before you sing seems to be a great exercise.