I'm sorry you are feeling discouraged. The spartan race idea sounds pretty interesting! If you don't know anyone who is into it, maybe it's time to meet new people who you can train with. I'm pretty shy so I tend to do things by myself, on my own, but sometimes it's worth it to make the extra effort to meet new people.
Also, congrats on being so near your weight loss goal! The closer you get the longer it can take to get the pounds off. I guess what I would do if I were in your shoes would be to continue the tracking of food & exercise like what you are doing now, but maybe focus more on the race goal and/or meeting new exercise partners. When you complete the race you'll have a success under your belt and if those last 10-20 lbs are still there, you can renew your efforts to lose them.
My Sparkpage is set to private, but I'm open to SparkMail!
"People often say that motivation doesn't last. Well, neither does bathing--that's why we recommend it daily." - Zig Ziglar