I can't be for sure, but unfortunately it sounds like your HDD is busted.
When big problems (not small problems like bad sectors) like your HDD bearings or motor give out; if it can be repaired, it is generally very expensive and difficult. However it may be possible to have it done as long as your platters still contain your info. If your data is that important to you, I believe On Track Services is a company that specializes in this kind of thing (like trying to recover data from HDDs which heads have crashed).
Benchmarks don't lie :-)