How to manage anger?

Talk to your doctor and explain what's going on. Not to get medicated (although that should not be totally off the table), but rather to get a medical clearance for exercise. And then look for yoga classes near you, maybe something you can go to on your lunch hour or for a half hour or so before you start the commute home.

Oh yeah, another thing. When I used to commute on a nasty road, I talked to my boss and we agreed I could come in early and leave early. It was super-early, I might add, as in, I would often walk in the door at 7, 7:30. That's not feasible for everyone (and these days I often wonder how I managed to do that), but it meant my commutes in both directions were super-fast. TIVO anything you want to watch because this schedule also means you go to bed at 9 at the latest, because you have to be up at like 5. I also used to shower the night before, which may or may not work for you. The disadvantages were that I had a dark morning commute unless it was summertime, but going home early often feels like a vacation day. And a one and a half hour commute was cut to something like 35 minutes. Wintry days, though, had icier conditions, so be aware of that. Used to see wild turkeys in the morning, too (I'm in Massachusetts). It's an option if you can do it and if your boss agrees.

As a former customer support engineer I get it. I tend to explode with anger and fury and still do sometimes. Sometimes you simply can't handle the stupidity. But the thing is that you need to seek a professional who will assist in finding your pain spots (which are not usually related to obvious things, like work or road rage). I will not recommend you to switch jobs before you get into therapy simply because you will drag the issues with you to a different work environment. That can help in 0.02% cases

For now, trace the most heated moments of the day and look for connections like the very same client or colleague you can't stand and why. Check for triggers that setting you off like places during commute or someone's set of views.

do you smoke weed? if not I HIGHly suggest giving it a try. A nice hybrid or indica will calm your ass down. Good luck!

... and give you psychotic episodes as well. Don't do it.

These are really good ideas. You can address some of them by possibly trying a different route for your commute or determining if there's a way to either work with different customers (trading with a colleague, perhaps?) or managing the communications differently. In a different job, I got saddled with one particular client who my boss couldn't stand. She liked me. Go figure - and everyone was happier once I took on that client and gave my boss one I didn't like. It's not always feasible, but it's worth exploring at least.