With the condition of the engine bay., It seems you dont drive on petrol at all, Try to convert the car to petrol atleast 3-5 kms before you reach home, And convert back to cng after starting and driving 3-5 kms on Petrol.
Since its not an EFI, The car wouldnt even start on petrol.
The fuel pump issue seems to be "jugarufied", because of the dirty fuel tank or maybe to switch of petrol on CNG.
Please post fresh pics of the engine bay, if your cars in running condition now, And what was the expence of your project?.
PS: Can you ask your mechanic to get a list of jobs done?
Engine out, Engine in, Replacement parts, Old parts, Jobs done and costs.