Going end over end WAY too often...help!

Sounds like your a bit big for the bike but it might be your riding style as well. I was going to suggest getting a shorter spring on the rear to throw the head angle of the bike back a bit but you may end up bottoming the rear shock out. Try fitting heavier springs to your forks so they are less likely to sag.
Could it also be your just not used to how the Stinky performs yet? Its a pretty huge difference comming off an XC bike onto a mad DH/FR rig. Try dropping your seat (watch it doesnt hit the rocker-arm) and slide it back so your weight is set back further. Hope that helps.

I'm 5'8" and 145, and ride a small XC or DH/FR frame and never had a problem with going over the bars (unless I hit something:p ) Take the advice of the other posters and also have another rider analyze your riding style. For example, you may be leaning forward a bit much for steep sections. DH/FR rigs handle a bit differently from XC bikes and require a little bit of tweaking in your riding style. The reason you feel like you are way in front of the hbars is because of the shorter stem and slacker head tube angle. This also why the bike feels good on steep sections (the bike was intended to point downhill🙂 ). Sounds like you are having a blast though, so have fun!

Some good points made above, and I'd also add that as you're still getting used to riding DH/freeride style, you need to get more fluidity in your standing up position on the pedals, so that when hitting stuff, the natural movement is to drop your weight back/behind the bike.

Also the same sort of thing often applies to your arm position/rigidity... when hitting rocks/logs/bumps you might find that your arms are still quite rigid (as they often can be no problems during XC riding), and need to instead be a bit more fluid in their "soaking up" of the bumps etc.

That combined with the weight naturally at the back of the bike should stop most of the nasty endos...

As with anything, just practicing will usually iron out most difficulties you're having - Good luck 🙂