Uav's are not used alone in the battlefield but have multiple supporting platforms, if a J8 is found to have taken off from a airstrip other jets would be scrambled to intercept it.
It's a catch 22 situation if he is released you can bet the masses will take to the streets burning US flags and shouting down with zardari on the other hand if he is not sent back it would have wider implications on the 'war on terror'
You are a sovereign country, yanks cant even bomb N. korea or Iran how they gonna take on Pakistani which has over 100 nukes they would piss their pants.
Not true during the 90's while US sanctions were in place we had no choice but to develop indigenous tech, dual use items were denied to us unlike China.