[Mike_Brace]

1) Yes these are better shocks and lowered springs. Mark position of existing strut.
2) Yes - but get it set on laser equipment - makes a lot of difference to the handling.
3) On the n/a the 80-82 B23E from Glts gave 140 bhp but the B230Es rev more freely. Most powerful n/a is the 16v but not a bolt in conversion.
4) Howe long is a piece of string? How much lead comes with your right boot? How much city driving? Figures seem to be from 20-35mpg with 25-28mpg probably being typical.
5) You are unlikely to succeed by the method you describe. Really should have been slackened on car. The best answer is to take it to a garage or tyre place and persuade them to use an air impact wrench on it. (If you have a spare £350 Snap On do a good cordess impact wrench that equals any air one - great if you have a lot of use for it especially away from a compressor)

Mike