Welcome to Smogon! Take a moment to read the Introduction to Smogon for a run-down on everything Smogon, and make sure you take some time to read the global rules.
I don't have an idea on critical capture but I noticed it never popping off when I was hunting HA Heavy Ball Beldum (with full Pokédex). I assume the chance is roughly similar to the catchrate in itself.
Sleeping turns modifier to 2x. Which upgrades Heavy Ball's catchrate to a whopping -14 instead of -15.5. So yeah, might as well Paralyze to half the turns it can do anything and stop it from calling partners.
Well I just looked it up, the CC chance is ROUND.DOWN[(CatchValue * 2.5)/6] (if best modifier is available, as you need 600+ for this but I dunno if this has been adjusted for Alola's limited dex).
Because of the rounding and even in the best case scenario (ie: CatchValue is set to 1) it would still round down to 0. Hence, no critical captures can occur.
Sleeping turns modifier to 2x. Which upgrades Heavy Ball's catchrate to a whopping -14 instead of -15.5. So yeah, might as well Paralyze to half the turns it can do anything and stop it from calling partners.