That grapple mechanic needs something more to feel like the crocodilian death roll which is entirely more violent than simple restraint. The victim should be knocked prone like in Pathfinder, and suffer continuing damage (automatic or advantaged following attack rolls by the croc?) until the grapple is broken. I would probably roll ongoing damage as the bite damage, but split it between piercing and bludgeoning, since a lot of it comes from being smacked around like a rag doll. Add drowning effects too if in water.
With the longer legs and serious claws, I'd give it the option to swap in a claw attack in place of the tail attack, one target - grappled or other, +8 to hit, reach 5 ft, 2D8 + 5 slashing. Either tail or a claw in a particular turn.
I'd make it CR5 like parent Giant Crocodile or bump up to CR6 for faster terrestrial speed, more potent grapple rule and claw attack option. Would have to play a lot more before I know if those enhancements are worth a CR point.
One last horrifying thought for your PCs. Crocs can and do climb trees. Google it, it was all over the news last February. Probably disadvantaged while climbing with its claws busy holding on, but so are most fleeing PCs.
And I'm still waiting for a boarcroc model. May have to try sculpting one myself, maybe by adapting a 6" long toy croc by doing longer legs and the pairs of bigger teeth.