Andrew Coggan has a good article on Power Training Levels that provides good descriptions of the various training levels. Basically you shouldn't be doing what you've classed as intense intervals on consecutive days. You may be able to but you won't be going as hard as you should on the 2nd day. It doesn't sound like you have a huge volume so I don't think you're at risk of overtraining. If you build up at a reasonable rate, a young guy like you should be able to train 20+ hrs/wk and I don't think you're there yet.

Ideally, you would get a powermeter but in lieu of that, since you have hills to train on you should be tracking your times on the hills and you should be seeing an improvement. If you start to have trouble hitting your target times on particular hill segments then you may need to take a day off.