1.Stats: Should Crawdaunt get a stat boost, Evolution, Mega Evolution or nothing?
Crawdaunt has 468 BST, and the largest BSTs a crab has are 478 and 500. With this in mind, Crawdaunt can get +10 BST at minimum, and +30 BST at maximum.
This will be helpful, but not by much. Crawdaunt is lacking severely in Speed department, which requires a high boost. An Evolution could potentially bring it, but there are no crabs that evolve for three stages.
A Mega Evolution is inconceivable without a stat boost first.
2.Should Crawdaunt get more abilities?
Pressure, Shed Skin, Sniper, Super Luck, Sturdy, Swift Swim and Tough Claws are abilities that can be added.
3. Should Crawdaunt get more moves?
Yes. Crawdaunt is missing a proper Ice move like Ice Fang and a move to buff its Special Attack like Nasty Plot. Other moves like Poison Jab, Shadow Claw, Psycho Cut etc. can be granted to buff its weak coverage repertoire.
4.What additional typing Crawdaunt can have?
Outside of Normal and Ice, Crawdaunt is heavily associated with Poison, Rock and Fighting.