WOW!! Eric, you've got something GOING here. What better reward / consequence than more or less RUNNING time?? Most students HATE to run in P.E.
One thing for you to remember-- 9th graders are still kids...just bigger ones. The "Oh yeah!" and "Awwww" or "Booo" is a way to keep them on your side so it doesn't become a war. Of course they will roll their eyes and act like it's childish-- they're supposed to-- they're 15 year olds!

But secretly, they'll remember you as the goofy gym teacher who turned classroom management into controlled fun.
Another thing to remember when you're feeling intimidated -- who the heck cares if a 15 year old looks at you like you're a dork??

Trust me, if you are consistent with it, and if you keep it a GAME and not a WAR (biggest mistake new WBTs make), it will work. Guaranteed. Promise. Cross my heart, hope to die.
Now. About the whole traveling around thing... that is tough. I'm a mobile teacher... I'm always around the room...so I hate walking allllll the way up to the board. A couple ways you can address this -- you can designate it to a student -- the class takes care of their mighty cheer or mighty groan right away and the student jogs over to the board while class resumes.
Another way is to carry something small with you to track it, and just update your board whenever you pass it, rather than going to it each time. Clipboard? little paper in your pocket? Announce what's happening "Point for you" or "point for me"...allow for the 1 second party or the mighty groan... and continue on. When you pass the board, update it for them to see their progress. Or simply announce their progress. "Oh no....as of now you have 2 extra minutes of running!" and ohhhhhh man 2 extra minutes is KILLER for alot of students!
MAN! I wish I could use running as MY consequence!!
Give it a try, let us know how it works.
Remember...above all... don't ever drop something before you've tried it for a month. If you try it, drop it, try it, drop it.... you'll lose them. Give it a month before you decide something is working or not.