[Shadowysn]

There are two seperate property types you can use: Netprops and Datamaps.

Datamaps may have a few hidden server values not shared with the client, although some/most others are also save values (netprops) at the same time.

You can dump datamaps in a similar way as you can netprops, by typing into the developer console:
sm_dump_datamaps "Datamaps CSGO.txt"

However, dumping datamaps will also crash or freeze your game.
It's just a side-effect of spawning every single entity into the game in order to get their properties. The datamap dump file will still be generated.

SetEntProp and it's other versions have a second variable you have to put in, either both Prop_Send and Prop_Data.
Use Prop_Send for Netprops.
Use Prop_Data for Datamaps.
Otherwise, you'll get an error in-game if you use the wrong property type.

From what you've said, m_bArmed may be a property that just makes the particles appear to clients, and doesn't pertain to anything else gameplay-wise.
Have you tried m_bIsLive though?

I've barely tinkered with grenade netprops, and the bumpmine seems to be derivative of the base grenade so I don't think I can give actual advice, but as a last-resort you might need to use an offset or signature of the function that makes the bumpmine live.