Hi,
while I cannot give you any values for the levels because I actually still don't own a DM10 module, I can anyway speak from past experiences with different Alesis modules.
Try vary the Xtalk values until you get a "decent" result for your needs. I mean: even if a
VERY small sound of any near tom is triggered when you hit the tom you wish, it is not so bad - to me.
Every drummer coming from an acoustic kit will tell you that a
perfect acoustic isolation does not exist - or it depends heavily on how much you muffle (or "choke") the drums' heads. Also, it depends from different and physically isolated mounts onto which the toms are set.
With acceptable and non-'invasive' small sounds coming from the toms, the whole electronic kit will sound a little more "real".
But this depends totally from your personal tastes of course!
The best thing to do is experiment wildly. Also, if you play in a group and not alone, try to hear how the kit sounds when the whole group is playing at regular volume levels.
You could have some surprises!