Around town is anything from 0 mpg, when you're stuck in traffic, upwards.
On a run it should be 50 mpg or better, unless you're thrashing it.
Panda brakes aren't the best, but they shouldn't be spongy: firm pedal, and if you apply full effort you should lock
both front wheels.
The sliding caliper on the front needs to able to slide (they corrode up) and FIAT pads are hard.
I have Pagid pads on my (non-servo) CLX and Bosch on the CL. Which are both OK, and a lot better than they were when we got them.
Have a search on this site: there are other choices, like Greenstuff..
New disks help too, if the originals are corroded up.
You can fit the servo from a 4x4 Panda, but it's a fairly major operation.
Start by bleeding the system, and hope you haven't got a knackered master cylinder: they're in short supply now
Regards
John H