I don't think you're going to be able to achieve your expectations with that battery pack and motor combination.
![Sad :(](https://goldenmotor.com/SMF/Smileys/default/sad.gif)
According to the Dynomometer results, the HSB 48V 1000W motor would be drawing around 25 Amps at 45 km/h
(363 rpm on a 26 x 2.00" tyre).
That 11.5Ah pack would only be able to supply 25 Amps continually for approximately 0.44hr before it was fully exhausted, which would give a range of less than 20km on a level route.
I estimate that you would need at least 14.5Ah capacity to complete a 25km trip at 45km/h without pedalling on a perfectly flat route without any stopping/starting and no headwinds.
Riding at full throttle without pedalling will reduce the range considerably, so you would need to restrict your maximum current and/or ride at a slower more efficient speed in order to obtain a longer range with that particular battery pack.
Alan