Strengthlegacy

Is the guitar just a little out of tune? I think it would help your vocal performance if there was a perfectly tuned guitar. Something weird is going on with the tuning and it would throw off my voice.
 
As for tips for improving the lower areas of the voice. For me I have two things I've done significantly. One is to take vowel like in between 'oh and ah,' kind of like 'awwww' and experiment with adding as much resonance as possible, then decreasing resonance to minimum. Try to make the timbre it brassier and brighter or darker and murkier.
 
So basically try to learn to swell and decrease the resonance, and sing bright/dark it helps a lot with lower notes. Listen to Frank Sinatra.
 

Well you're doing a good job man. The way you can hit notes while doing almost an exhale scream is something few people can do well! Keep it up!

That's okay, I'm american and my accent is a bit weird when singing english songs, too.

Never make excuses. Step up, represent. If you had a cold, okay. But you always do the best that you can, regardless, though I don't advise singing with a sore throat. When you give excuses, you give a reason for people to expect you to fail. So, don't.
 
I know others will say it doesn't matter as long as the vocal folds are not inflamed but sometimes, with discomfort in the throat, you start compensation by changing something else, like breath support or good placement in order to not flex the muscles in the area of the soreness which will affect how you resonate.
 
You changed keys a few times. That is, you started the song in one key or with one root note, then changed a few more times. So, work on your intervals, distance between notes. But I could hear you putting in a little style, a little r&b trill here and there. Before you worry about that, get the interval of notes right. Then, later, you can noodle around and be able to return to the the true note in whatever part.
 
I think the last key change was so that you can do the top note, which you did at least half an octave below the traditional arrangement. Francis Scott Key wrote a beast of a song and was not, himself, a singer.
 
You don't have to sing in the original key. But pick one and stick with it. But you have a good tone of voice and you have the lyrics and timing right.

It's okay, you have a goal in mind with the sound of Adam Levine, fellow member videohere admires most Lou Gramm. It's not a bad thing.
 
Instead, try the advice and see if it helps, or not.

I think did better on "I'll Be" and "Sugar" than you do on payphone. For whatever reason, your voice sounds better on these. Which can happen. You sound good covering one song by an artist. But not necessarily on another song by the same artist. Not that you did badly. Just, if I had a preference, it would be these two songs, especially "I'll Be."
 
I am not a big Adam Levine follower as far as music though I like his thinking about it. But I do like him as an actor.

That's a really distinct timbre. It is growing on me the more I hear it. It's a bit on the nasal side. For acapella the song is recognizable and mostly in tune which is good.
 
I think on average balancing out the resonance to include just a bit more of the lower/warm side might help you get a little more mainstream, but Adam Levine is pretty nosey as is.
 
The opposite extreme of resonating is a very open throat, lower tongue, and high softer palette. If you were to say like 'hoooooo.' Like an owl and almost yawn the beginning of it it would be the polar opposite, which would be too far for most mainstream tastes too. Either way, higher tongue generally helps, even with more open throat.
 
I don't know what timbre you're after, or what your artistic goals are, but I'm thinking just a little more openness might add a tiny bit of richness.
 
On a side note, dude you're like almost eating the camera, you're so close, hahaha. Just thought it was funny. Most people are like camera shy and would put a bit of distance or whatnot. You got balls. Your face takes up my whole screen.