Route image is 0 to 100, I find you need 60+ to get a nice sensible LF
You also want to do some low level General Marketing to get your Company Image (CI) up, for Y-class low levels are fine, but more is better - I operate regional stuff very happily at 50 CI,
The length of your flights can be a factor if you are using HD seats, pax don't like them beyond 2 hours each way... it's not a big effect, but maybe look at refitting to standard seating on longer routes, while doing that you can also install a few C-class seats (4-6 seats I'd suggest, assuming you have some C-Class demand). These should fill gradually as your CI rises.
Yield c/RPK = Revenue Passenger Kilometres, i.e. cents earned per ticket sold, per kilometre flown
Revenue c/ASK = Available Seat Kilometres, i.e. cents earned per seat (sold or not), per kilometre flown