not a bad singing GeKo at all, just keep on practicing!
However I wanted to put some points about practice. Thing is that our voice chords are muscles. And in order to get maximum out of them we must train them. And by training I am not talking about just singing songs, but special exercises. Think about basketball players - before they start playing, they have overall physical training to prepare, like strenghtening certain groups of muscles, to build stamina and strenght to use them in the game. Same goes with vocal. There is plenty of material availbale for free and for money, but general exercises are build around working out your range (so that chords should have enought power in all of your range and of course increasing your vocal range too), stamina (to keep up for long singing, not just getting sore throat after three songs) and technique (vibrato, stacato), breathing (this is the key thing to get right first). Then you have to feel your voice's registers (head voice, chest voice, falcetto, etc). And then you are set to sing songs 
Of course theese things can go at one time, step after step.
My recommendation would be to setup concrete practice routine and stick to it (think about running - you do it three times per week, and after few months you get better and better). It can look like this: 15 minutes warmup exercises, 20 minutes workout, 25 minutes singing song.If you do it regulary and without fail and excuses, you will definintely see improvement after a month or so and it will get better and better by time.
I am not a pro singer now, but in my school times I was singing in very good choir (european awards winner), and we had special "voice setup" lessons twice a week to put our voices right, so thats how I know it. And after 15 years of break I am working to get it back on track, and above practice routine works for me very well. The only issue I have - I am baritone, and I can't sing Joe's songs (they are generally too high for me), but then I can do Sinatra, Elvis, Veiland, even some Chris Cornell (black hole sun), etc.
Talking about Joe's interview where he mentions he found difficulties singing when he had lost weight, I can add this - vocal chord muscles has the same structure as your heart muscle. One doctor even prescribed same food supplements for our vocalist when he found issues with his voice as used to strengten the heart muscle. The issue with this muscle as well is that its VERY sensitive to stress (remember stories about vocalists loosing their voice after some major shakeouts, e.g. Kallas?). So fo Joe first I thing the major issue was to get over his personal problem to make voice work again as before, and diet is a stress to human body too! I also have been on a diet three years ago (lost approx 40 pounds) and had same issues. When you are weak, your voice is even weaker. So I mean good mood is good for singing!
Today is a great evening here in Vilnius - I will go to Joe's gig, will post impressions tommorow!
