Without checking the size of the intercooler or the setup your working with, i would state the generally accepted terms.
1) Its better to have a hood scoop regardless of the intercooler size, but in your case it will not make a difference. Given the small size of the engine bay, the engine heat does not have a lot of space to disperse, your cooler would be running rather hot in the bay plus it would make things ugly unless your willing to do tiring work of sorting the engine bay properly.
2) You should mount the intercooler in the front. Hood remains as it is, you would need to route the piping for the intercooler which might get very congested. The longer pipes should hardly cause any difference in boost response.
3) Is it the stock turbo? Any pictures? Any shaft play? Condition of the internal wastegate? Cannot say anything until and unless you tell the condition of the turbo.
4) Fuel economy would more or less be the same regardless of where you mount the intercooler. Rest depends on your tuning and driving style.
I hope your doing something about the suspension and the brakes.