Riding long distances isn't the be all and end anyway. Despite my sig line I much prefer a nice ride to a long one
That looks like a nice bike, I hope you enjoy riding it. If you enjoy it then you will improve just by riding it more
As for riding up hills, there's nothing wrong with bottom gear. If you want to improve on a hill then ride as far as you can before you have to stop and walk (if you can ride all your hills in 1st gear then try 2nd). Then remember a mark - something like a lamp post or drain cover - and try and ride past it next time. Slowly your legs will adapt and you will be able to ride up hills you don't think are possible now.
With the saddle, do you like the one on your other bike? If so try swapping them over for a bit. The more you ride the less sore each ride will be though. I'm not sure if you break the saddle in or the saddle breaks your bum in but either way it gets more comfortable eventually.