against snake, dno't try to knee him out of his up-b. either dair him if he's below or in front of you (because the dair that sends them away is actually useful agianst his recovery) and watch his percentage because it may take a few dairs to kill him due to his recovery being so good and hit stun being garbage.
if he's in front of you or above you, up-b him. the grab hitbox on it is huge. but try to do it in the early frames when he starts the up-b, because if he drops or aiddodges off and you miss the cypher (aim for the cypher) then you'll die.
of course use the stuff from above too, but a couple more tips against snake would be
-Be careful with (grounded) falcon kick. do not use it at low damage because he'll either land and ftilt you, or bair you. if he's at a good amount of damage its pretty safe move if he doesn't block it.
-at 0% and maybe up to like 5 or 10%, you can falcon kick snake from above and it'll do like 23-25% damage. if he blocks it you're ****ed.
-approach with grabs a lot becuase if he shields any of your aerials its a free grab or ftilt for him. don't ALWAYS try to grab though cause he may spot dodge.
that's just a few things off the top of my head. for the 'grab knee off the stage combo' do you mean dthrow to knee? cause i never land that ****.
oh yeah and kill moves against snake. upsmash kills probbably at 120% maybe. dsmash is good too and i use it personally for punishing rolls but i don't know the percentage for killing him off the top of my head. Knee if you use it at the right time. uair will also be a semi-common kill move since he doesn't really die so once he hits the usual 180% a uair may kill him LOL.
try to gimp him whenever possible with the dair, but don't be too jump-off-the-stage happy because you may jump right into a nair which does 28% fresh.