I saw your car at Khalids and it is a real gem. I am glad you have brought it out for restoration and I agree that Arshad has done a great job. His main problem was time management and it seems like he has finally got his act together. My Oval is waiting in line for its turn as is Shazadi - my GT beetle. Both cars would be restored at Khalid's and the body work performed by Arshad.
Answering your third question first...a disk brake system is superior to the drum brake system but the drum brakes in a beetle are in no way inadequate. I have driven cars with drums and never have felt the need to convert. I do have disk brakes in my GT beetle and my Karmann Convertible but I hardly feel the difference when I am driving my 1960 with drum brakes all round. Maybe if you have a 1.6 engine then you can start considering disk brakes but if you check the condition of the drums and replace if worn out you would get the same stopping power as the VW's with disk brakes (or close enuff) Billo, my 1960 bug has a 1.6l engine and drum bakes all round. I have not had any issues cruising on the highways in the US and Canada at 120 km / hr or in city driving. All four drums, however, are brand new, as are the wheel cylinders.
The disk brake conversions if sourced locally would be beat up units that have seen better days so not necessarily an answer. If you must, then go for a brand new kit or a used kit that has good rotors and serviceable calipers.
Your second question re. seat issues has already been answered by rebel. Zaheer ustaad is good even though Mian Jee in G-8 Islamabad has done a lot of work for me and I have never had any issues.