You are correct in regard to the m_fJumpSize, this value affects the amount of jump of your weapon due to recoil. However, this is not he only variable that affects the accuracy of your weapon. There are several other variables that increase or diminish the accuracy.
m_fErrorMaxSize is one variable that influences accuracy. This is the ammount of error (inaccuracy) that is tacked on to the aiming system's trajectory for your bullets.
m_fTimeToShrink is another. This is the ammount of time that it takes for you weapon's aim to return to its normal accuracy after the error is added in.
As you hold down the trigger, the ammount of error and the amount of time needed to return to normal accuracy increases.
You might consider the strategy of using short controlled bursts of fire, ratherer than long continuous full auto.
For the wound/damage variables, I have not experimented extensively with them. Some variables affect the damage you inflict, while others affect the damage you take. You might find that it is a double-edged sword in that if you change a value, the game engine might give another player who is targetting you those values, so the damage they do to you is greater.
In terms of the values being overwritten, or reset: The game unpacks the umd file regularly. The first time the games is run, or whenever the cache on x,y, or z is deleted, it will put a bunch of files on the cache drive to speed things up during the game. Parts of the user.ini file that exists in the system folder do get re-written when you change button configs and profiles. The values for the buttons (Joy1 - Joy16) ,for example, in the user.ini get re-written from the controllerconfig.ini that is embedded in the umd. Conrtollerconfig.ini has the sections [ButtonConfig1] and so on, that correspond to the button set ups in the game's options menu.
Your best bet is to get the unpacked umd or unpack it yourself - putting the unpacked files back on the xbox hd, and then remove or rename the umd in the system folder. Then, you can edit the actual configuration files with an ordinary text editor, like Notepad.
The file that contains the variables you mentioned is R6GAMESETTINGS.ini which is embedded in the umd. You may find that the settings you change work fine in single-player, but do not work the same or do not work at all in multi-player. The reason is primarily because the host server xbox of the game controls many of those variables. The server wont allow or will not use those values that are outside of the standard value ranges. Some do work, but others dont.