Coming from someone who is struggling to even find a job and has to work an on-commission at-home telemarketing gig that feels like I'm prostituting my soul - please do not quit. I only say that because I can tell you just how hard it is to find any decent jobs out there right now. It's an every-man-for-himself brawl out there in the economy right now just to find a job that pays over 25k. You have a LOT of experience and maturity, and like you said, you're getting paid a pretty penny - that's a BIG DEAL.
You are one of the lucky ones who are earning a good pay check. Practically all of us out here who aren't so lucky are practically drowning alive.
Is there anything you can do to make your job more tolerable? What about not taking anything the caller says seriously or personally, since all they hear is a voice on the other end anyway? How about looking at your job that is "beneath your intelligence" as being easy and less stressful? How about doing little things to make your day worth while at work? There's a number of stress relieving things you could do at your desk.
Think about all the people who can't even sit down at their job. On their feet 12+ hours a day and they aren't young. That's literally something I have to think about to make me feel luckier about having my stupid job. If it's really that bad to where you can't stand it anymore, keep going on interviews and finding positions that pay wages closer to what you're earning now.
The fact that you can even go home some days whenever you want or whenever the weather is bad is a god-send by the way - that's unheard of anywhere in the corporate world.
How close are you to retirement? Maybe you can ask for a promotion later on and become the big brother who keeps an eye on everyone?