Hi three - have you done a DAFNE course yet ?
Ideally correcting in between meal times isn't recommended, simply because novorapid takes up to 4 hours to reach its peak so on DAFNE it's not recommended to either test again within this time frame or to take a correction dose as your not getting an accurate reading. This would explain why you are crashing and then having to take a snack. As long as you test before your next mealtime then correct along with your carb ratio dose this is fine.
I used to do what you did and ended up in a vicious circle of going high hand low so unless I'm driving and need to test I don't bother now, also using less test strips and also more confident with my diabetes, takes some getting used to but will also help you stabilise and if your moods are affected then will help to steady you.
I took this one step further to get better control and now low carb too so take less insulin and less room for error with doses, takes some getting used to but again helps stabilise and promote better moods, I also don't hypo at work anymore (or very rarely now).
Good luck it's work in progress as I always say !!