Vocals in metal / rock is never an easy feat, personally the amount of energy involved and power needed to bring the music out is vital because its genre lies in roots of strength, dominance and power. You need to have a lot of stamina to pull metal/rock/punk all that off very well..
I can't quite hear the intro of your live maiden cover, cos the cameraman was singing (quite badly, might I add!!) over your voice, but I think you've got the potential to bring your power vocals out if you weren't singing so fast. You can't pull stuff like Maiden off if you're gonna have to rush like that; you end up compromising vocals that need to be projected over the speed by which you had to sing the words. Most likely, to keep up, you'll end up growling, which also, in the end, cuts off in vocal power within keeping time. If it's your band who's asking you to take vocal lessons, you might want to suggest to them playing slightly slower (first) until you get the hang of it. I know the feeling shiok lahh to play fast, but tackle your problems first before enjoying yourself...
On the "Dying In Your Arms" cover... like btherl mentioned, some parts were strained and pitchy, although your tone is pretty much there already. Curiously tho, were you were recording your vocals whilst playing guitar, or were you were focusing on the guitar parts whilst singing at any point? I just have to ask, because it appears that you're both a guitarist and vocalist.
Two things imo, which might help reach that "power" you need in your vocals is a good balance of projection and vocal feel.
What I mean by projection here, is that you have to imagine (prep yourself before singing) that you're facing a full audience, and your voice has to reach the guy wayyy at the back. Like I mentioned, I think you've got potential to do that, it's just that you might have compromised your projection over keeping time, and end up swallowing the "power" instead it letting it all out. Once you have achieved enough confidence to pull that off, focus on your feel -- be more confident and let your aggression out. Listen to the lyrics, understand what it's about and how it relates to you, and pretend you're just screaming to tell everyone how you feel (But don't literally scream lah k, you'll freak the fella out). Once you've got these two covered, balance them out with a good amount of half projection and half feel.
Under the circumstance tho, that you HAVE to sing fast, bring out your vocal feel more; since you're playing metal, . So far on the maiden cover, I think you've done a pretty good job with the vocal feel, just that the speed you were singing cut out the vocal power.
Good luck~~
ps. I'm still learning on vocal power as well, and personally that "imagining you're reaching the voice to the guy way back in the audience" imagery helps improve the vocal power :} You might wanna try and see if it works for you too.
The yelling part has a lot of energy, that part sounds good! Doesn't sound healthy though.
