Did you get your tank cleaned?
From my experience of Santro
Don't change fuel pump, nothing wrong with that. What make fuel pump failure in CNG/LPG is lesser usage and rust.
Finest rust passes upto injectors. You can check images in my thread https://www.pakwheels.com/forums/d-i-y-projects/211384-rejuvenating-santro. Lesser fine rust is held at fuel filter and pump sieve. If pump sieve chokes, it deprives pump motor of fuel, resulting in low pressure fuel.
I have been using same fuel pump for past 6-7 years, only sieve changed and tank cleaned frequently (once a year- after monsoon). Even serviced motor
For fuel leakage, I had same problem when I cleaned motor and refitted it, later found drop in pressure, on test bench I found that delivery pipe from motor (spring type) was loose being of pvc and leaking fuel back in insid pump, so I cut it from top and refitted with heating on stove and used clip to secure it, now pressure was normal.
Hope this helps.