Right off the bat, you ought to go read up on Masashi Kishimoto and all the work he did before he started on Naruto; there's a good summary on his Wikipedia entry. Keep in mind, also, that like a lot of manga artists he has assistants to help him out with things like inking and backgrounds. Working all on your own, writing and drawing, it's not realistic to expect to be able to match his output.

Before I ramble on too much, I'm also going to suggest some books that I'd consider required reading on the subject. You may have already read some or all of these, but they're the big ones:

• Scott McCloud, Understanding Comics and Making Comics. The second book of the set, Reinventing Comics, isn't really necessary for the stuff you're looking at. It's interesting but it's pretty easily skippable.
• Will Eisner, Comics and Sequential Art and Graphic Storytelling and Visual Narrative. Particularly the first one. Sequential Art was my bible back when I was in college.

You might also find The DC Comics Guide to Writing Comics useful, but I'm going to talk a big about the salient part of that here.

To answer a couple of your specific questions first, though:

• Many comic artists use reference from time to time. Some go way too far with it - we're talking Greg Land territory here - and others don't use it at all. In his figure drawing video for Gnomon, David Finch talks a little about using photo reference, and mentions that he doesn't use it for his figure drawing at all. Alex Ross is at the other end of the spectrum; he uses extensive photos, but unlike Greg Land he takes them himself and doesn't just trace over stills from movies or porn flicks. I think you'd find most are closer to Finch than Ross; they've drawn enough, practiced enough, that they can create from scratch, but will bust out a reference if their stuck on a particular pose, can't get the foreshortening quite right, etc.
• I couldn't possibly guess how long it took to get those particular pages done. Ultimately it makes not a bit of fucking difference how fast anyone else can get their work done. Your pace will be your own. As you get better at it, you'll go faster. The only way to get better at it is to do lots of comics.
• Rather than copying another artists comics, here's an exercise for you. Look at some comic book scripts for comics you haven't read but can get your hands on. Here's a site with a bunch of them.. Pick one out and draw the first four pages from it. This isn't a drawing exercise, specifically, so you don't need to do super-clean, finished drawings; just keep them rough and sketchy, but polished enough that you can see what's happening in them. Then look at the original and compare yours with it. Again, this isn't a drawing exercise, so don't compare the drawings; look at things like the layout, the way the panels are framed, where the artist used closeups, medium shots, long shots, etc. Study it carefully, frame by frame, to see what choices the artist made vs. the ones you made. Then do it again with the next four pages, and the next four, etc., until you've done the whole thing. Repeat as necessary with other scripts.
• How long will it take you to where you can just crank out comic pages? I don't have a clue. Neither do you. Neither does anyone else. It'll take as long as it takes. But you'll get there sooner if you start now. Start drawing, immediately, every day. And draw comics right away too. Bad ones to start off with, but they'll get better as you go.

Now when it comes to actually figuring out your pages and panels, you've got to start with your story. If you're working on your own stories, you're at an advantage; you don't have to do a full script, like the ones on that page I linked above. You can just do a plot-first script. Basically, it's just a rough outline, page by page, of what happens.

That's how Stan Lee used to write all those comics for Marvel back in the day. He'd sit down and hammer out a plot, usually just sitting there with the artist in his office, and send them off to pencil it. Then they'd give the penciled pages back to him and he'd figure out dialog to match their drawings, scribbling it in in pencil. Then it'd go to the letterer, then the inker, then the colorist.

That's about all I've got time for tonight. Hope some of that helps.