7mpg in a R32!? What the hell were you doing with it?
Mkiv Supra's were either n/a or twin-turbo; any single turbo mkiv will be an aftermarket conversion - i'm guessing you mean twin-turbo when you say single turbo?
Your insurance seems mighty cheap considering your age, i'm having a guess that the quotation that you have had if for a UK spec car - J-specs will be substantially more expensive to insure. Worth taking a look into
Answers to questions:
1) use the search bar its a very common question (remember that the Supra isnt really a 0-60 car, its more of a 60-180 kinda car!)
2) You can buy a really tidy manual N/A for under 4k, or you could buy a dog of a TT with an auto gearbox. For your average BPU auto TT you would be looking to budget between 6-7k
3) Use the search bar - there is also a Supra guide on here that explains all the different model types. Worth a read
4) You can buy an N/A for under 4k, but its not worth the extra expense of converting it. If you want a turbo, but a TT
5) The rear seats are vinyl, GZ and UK spec cars had leather front seats
And a foot note; if you decide to buy a TT, it WILL cost you a great deal more to service and maintain than your Calibra and R32 combined