Well to start with a dumerils is not a common boa.
In the wild a baby common boa would not put himself in that situation. There is LOTS of cover in the jungles of South America. If they do get in that situation, more than likely, they wouldn't survive. That is kind of why boas have so many babies. many will not survive to adulthood.
As for finding water, food and humidity, again its the jungle so humidity will be high to begin with not to mention under the jungle floor it is probably pretty humid. Water, they can find lots of leaves with standing water in them I would imagine. And food, well boas are designed to go long periods without food but i'm sure they find their fair share of little critters in the stuff that are also hiding from bigger predators.
And finally, every animal will have its own personality. Some are more outgoing while some are more shy. Some are more defensive and others more passive.
And may I ask why you are evening putting a baby snake on the middle of the floor? A bigger snake I can see it as a snake like Rosey my 7' BCI or Vicky my 5' BCI or Caesar my 5' retic, you can put them on the floor and they will be fine although even them I don't put in the middle of the floor. I always let them hang on me or sit on me while I lay in bed watching tv or whatever.
And finally I'm assuming when you say 'red tail' you are referring to a common boa aka BCI and not an actual true red tail like a suirname, Guyana, Peruvian etc? Because doing that to a baby one of those can really stress it out and create problems.