Christians eating venom and not dying/human existence/christians often being happier/babtism results/free will/and so on, sure, you could say they have other reasons,well if eating venom was to prove god for the christians why dont all the christians practice this then, christians being happier than who? All the people I know and associate whit are happy as can be none are christians though. free will? who hasnt got free will? ohh young kids who have christian parents do they have a free will about having to follow their parents to church or not?
Eating/drinking venom doesnt prove a god at all, it aint only christians preforming that trick so why would/should this work for non christians as well.
Gravity exist within the core of the earth it pulls things toward earth, as long as none can prove otherwise we can say that gravity has been proven.
Now if christian wanna prove god, let them all drink venom and let see what happens, maybe that could be a way of telling the ones strong with faith from the ones who aint. Your arguments of christians eating venom could raise other question like why does christians die of diseases at all?