I don't have much experience with mixing and mastering aswell, so I'm not going to answer all your questions.
What I've noticed in your recording (I know you didn't ask about this, but I'll tell you anyway. lol.) is you mix sounds a bit unnatural because you pan everything to both sides. I think for the backingtrack this is not a big deal, since you can have two guitars playing the same thing. But the problem is that it doesn't sound natural. When two quitar players play the same, there are still going to be minor differences. When you pan two exact same recording to both sides the mix gets unnatural. I would recommend not to do this. Pan the quitars precisely the same. If you want to have to have fuller sound, record the quitar again and pan it to the other side. This goes for all instruments. Imaging how you would perfrom this song on stage and pan it accordingly.
When it comes to voice the above goes even more. It would strongly recommend not to pan your voice to both sides. It sounds as if there are two people singing excatly the same at the same time on the other side of eachother. This is impossible and your mix sounds unnatural as a consequence.
I think it's ok to double the tracks, but be carefull with the doubling of reverb. I ussualy double the 'naked' track and put reverb on the first. Then make the second one softer to the point where it sounds full, but not to full. Don't forget to pan them equally.
About compression: The idea is that a compressor evens the sound out by reducing the softer parts and lowering the loud parts. You can tell it from what point it should do so by adjusting the treshold. If the treshold is a -2 Db the compressor starts working when the mix/track exceeds -2 Db. You can adjust how strongly it compresses by adjusting the ratio. There's much more to learn, but I don't know half.
Equalization: With an EQ you can control what frequencies you want to cut/boost. If you have very much low frequencies in your mix (bass etc) you can cut these frequencies out with an EQ. Again: There much more to know about EQ.
Normalization: With normailzation you can control how loud the average (or peak) loudness is. If you set it to 0 Db, the average amplitude is 0 Db. This might be helpfull for you, since you have problems with different amplitudes in your mixes and between your songs.
One thing the video you posted differs in you recording in the panning. He has clear panning. That's why you hear his voice so clearly. There's nothing in the way. His voice has it's own place in the stereofield.
Like I said I don't have much experience with mixing and mastering, so I might have said some wrong things. But I hope it will help you a little.