Evgeny,
Great job.
Let's not forget the way this saber looked like when it came to you: it was a deformed lump of rusty metal. No amount of "gentle" cleaning would have recovered even a trace of what it was supposed to be, or prevent any further degradation.
To be honest: the historic and artistic value of this ( or any other) sword pales in comparison to Sistine Chapel.
http://msopal29.myweb.uga.edu/BeforeandAfter.html
If works of Michelangelo and Botticelli could be aggressively restored and conserved, a similar approach to a sword is fully justified.