Take it to a cylinder shop with a bench. They can break it loose and tell you the torque. Better yet have them repack it while you are there.
Some very good advice there
Unless you are really wanting to save a few bucks and your time is worth next to nothing
a shop can do a cylinder like that in less than a couple hours... full service.(provided they aren't backlogged a week or two)
Among some other benefits of a shop set up for these things, they can also hone and polish the can and rod while fixing any other issues that may be in there to make sure it lasts a long time.
They can also do a proper pressure test to make sure it is safe and 100 percent ready to do it's job
There is a lot to be said for having the right tools for the job, makes it nearly impossible to cause more damage to the cylinder wile trying to work on it... of course if you have some decent fab skills and are willing to do a bit of research it really isn't that hard to make any tools you will need
And most shops I have used in the past use good parts from reputable suppliers for the seals,wipers and other wearable parts... not some odd ball import funky rubber that leaks two months after you install the cylinder...
Anyways it really isn't that hard to work on these things... BUT you really need to know what you are doing before you start... there is lots of info around for those that wish to DIY it but remember it isn't something that everyone can do the proper way....