Those look good.
I think so.
Tactics: A sea bat often attacks stealthily, attempting to paralyze and swallow an opponent before its companions notice. Sea bats are canny enough to avoid large groups.
That'll work better, sure.
The original critter has a pretty fast swim speed also. Well, it's another point of differentiation. For tactics, maybe
A sea bat normally buries itself in silt and waits until it senses the approach of prey. It then burst out of the mud and tries to swallow and paralyze as many opponents as it can, and it is willing to pursue victims over distance if necessary. Sea bats do not attack large creatures except in self defense, since they are unable to eat creatures too big to swallow. They are canny enough to avoid large groups.
Works for me!

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.