"have very quick regeneration(Ik xeno's don't have regeneration) I wonder if Deacon can regenerate too."
Who knows.. from what i looked at into the movie, was these Worms are well Space Worms but maybe are similar to Earth Worms.. and they can regrow their body parts.. like a Worm Can.
The Black Goo, infected the Worms with Xeno related DNA, passed on Xeno traits (Acid Blood) while Evolving the Organisms best natural Traits (Regeneration)
"the Engineers would be more cautious about the Goo since they probably more aware about it and what it can do?"
Maybe the Engineers had stolen the Goo or re-weaponized it from something stolen...
It could be they was tasked with using the Goo to Sacrifice themselves by command of the Hierarchy, the Engineers or a Faction then rebelled against this like the Igigi did against the Annunaki....
They then chose to re-engineer the Goo to create something to use on their Creators and their creators Chosen Children?