Shave the head or change pistons. See Miata.net
You will have an improvement in engine performance and an increase in compression unless the compression rings on the pistons need replacement .
No you don't need compression to get spark but you do need compression for it to run.
motivation of lossless image compression
either too tight or to loose, need about 8mm of give between alternator and drive pulley
Depends on why there is no compression.
This depends, although most likely standard unless you have a Eunos model which is the European Miata, which those use metric.
Just over six quarts.
The higher compression the engine the more power it can theoretically produce. The compression ratio is mainly determined by the type of fuel being used.
If engine is losing compression it is likely the rings are worn and need replacing. The valves are likely leaking too and need replacing.
a diesel engine uses compression and has no need of spark plugs
you need to go to the dealer and get the factory code to reprogram it
Not if they are struts - need a spring compressor