Dude, you're 20 fucking years old. Are all job offers going to suddenly disapear if you actively persue music for a few years? I can almost assure you that if you take the security route, you'll start feeling all snug and safe, and never have the balls or the time to do any serious touring. You may live to regret either decision, but I think its safer to say that shelving the touring plans would spawn more serious long term regrets than shelving the job.
Picture yourself 5 years from now on either path, both in worst case scenarios.
1. You decide to persue the band thing. Nothing comes of it, you rack up some serious debt, you have some horror stories from being on the road with your best friends (maybe you lost a couple through arguments), and maybe its harder to find a secure job at that point for whatever reason when you finally do quit the band, and you end up on enemployment feeling like a loser.
2. You decide to take the job. You make a shit ton of money and have benefits, but you still rack up some debt, have far less time to devote to music even as a hobby because you have more responsibilities, maybe a house payment and a wife and kid that may absolutely ensure you can't tour. The worst part is, metal still is a huge part of who you are, so while your wife is listening to fucking Lady Gaga or some shit in the car, your headbanging days are reduced to putting on some death metal record she hates in a room in your "alone time". You go to concerts still when you can afford to stay out late, and watching the bands up on stage, while still enjoyable gives you a sickening knot in your stomach, because you're staring at the choice you could have made. Sure there's no guarantee that you would've made it that far, but you'd NEVER know because you never gave it a real serious push. You didn't exhaust your efforts. Then you go onto the sneap forum and make excuses why being in a touring band would suck and you're glad you quit persuing it, even though you're really just lying to yourself. (This is pointed at myself, referring to things I may have said in the past, not at anyone here telling him to go with the secure route).
To me, one decision seems to be a lot more permanent than the other.
I gave up on the band thing to try to sort of "grow up" and find a career. I regretted the fuck out of that decision, because I never ended up finding a career path I wanted to persue and just had an emptiness where music used to be, and AE shit and my solo projects did not even come close to filling it. I missed everything about being in a band, and even posted a thread or two here about being depressed about giving it all up. I even cried at night a couple times because I felt like I gave up on my dreams.
Luckily for me, my former singer joined a local band that we used to play gigs with, who already had a record deal, and when their bassist bounced, my friend asked me if I could fill in on a tour, and I ended up taking a permanent position in the band. Things still have yet to pan out, and I'm as broke as I've ever been, but I've already accomplished many of my lifelong music goals since I joined the band less than a year ago. I toured across the country (and had a shit ton of fun despite the van troubles and 16 hour drives and playing for 4 people at some places), I got to write a bunch of music for an album that's set to be released nationally, I signed a recording contract, I got to be in a music video, and I'm building memories I'll cherish forever. I'm broke a lot, but I'm much happier than I was when I was bandless and making decent money.
All of it was possible only because I didn't have a steady secure job to hold me back, and my fiancee is totally supportive of me and gets turned on when she sees me on stage (bonus!).
When you make your decision, make sure you consider which will lead to a more permanent situation. You can always quit a band at any time to look for a nice secure job. You can't just quit a nice secure job to go on tour with a band you may not even have in a few years.
My too scents.