key aspects of your controller/display combo is the 14a peak power rating and the led/dumb display unable to give a dynamic response. which indicate configuration changes are difficult to make without a dynamic display (LCD etc) and any unrestricted top speed would be limited by the 14a limit
There should also be a 3rd metric on your battery beyond the Ah/Wh in amps indicating the maximum drain it can sustain.
A new KT controller and display combo with a peak amp output within the capacity of your battery to supply is probably what you need to remove the restrictions embedded within the current controller/display. (ie a KT 15a sinewave controller with any kt-lcd display and plugs/sockets in line with your bike, some wire splicing may still be required tho..)
KT brand is popular as there is a wide range of lcd displays and the system is fully configurable, although the manuals are written in a special form of 'Chenglish' . be mindful not to invest in a controller that can draw more than your battery can safely provide, thats a recipe for disaster.. google for "kt lcd03 manual pdf" for a look see before taking the plunge
your looking at £80-100 for a controller/display combo, the higher rated the controller (peak power) the more watts it can push into the motor to achieve its max rpm/speed and a higher cost.
While i get wanting to own your bike and have full control over it I also have to ask Is it worth it? with a small battery matched with a 14a controller, its probably wise to stick with an equally small 15a controller like is fitted on most eu/uk complient e-bikes so your max speed unrestricted is probably in the 18-20mph range the last couple of miles being slow to creep up to on the flat with the wind behind you.. against which your risking your bike your driving license and in the worst case the roof over your head and any future financial security.. Atm plod are not doing very much about dodgy ebikes iirc something like 260 bikes were confiscated in a recent year total.. But that could change , all it takes is one high profile toddler to wander under an unrestricted bikes front wheel.
Not forgetting that bikes are bikes and are not designed for speed or STOPPING at higher speeds.. So if you do de restrict your bike remember to test your braking distances exhaustively before venturing onto the roads.
The other limit is the motor max rpm no matter how many watts you pump into a motor it wont spin faster than that..