Hey,
I noticed this problem when I'm setting up a mod in the server.. When you set the tf(Turnframes), mf(matchframes), ft(fracturethreshold) etc.. Then When I set the mod to sambo.tbm or classic.. It becomes classic settings so the previous settings you've done is useless and replaced to classic..
So the /exec command (for us server moderators) isnt working and again it turns to classic..

Also(The common Problem in 3.3 Multiplayer, So everyone knows this), The DismemberThreshold is useless because when you set it to 200,300,1000 etc.. It is only 100 DT when you dismember..

The dismemberment threshold will be fixed in the next release.

Regarding the mod: first load the mod, then play with the settings.

The setting are reset to classic (or any of the mod's preset gamerules) to make loading a mod deterministic.
(Meaning - every time that you load a mod - you get the same game settings)

In short - customize the gamerules after the mod was loaded