It's best to take a "rest day" from severe caloric restriction too, so that your metabolism doesn't just scale itself down. Eat the way you normally would on your rest days.

It's not necessarily about overtraining, it's that your muscles are literally torn to pieces during your workouts and they need rest time to rebuild and get stronger. Less so when you're young, but even so.

No one has mentioned focused strength training - that's what I see as being missing. You don't need to get super muscular on the bike, but some leg work at the gym will definitely help.