f-tilt->no
fait->no, it sends up now
bair->yes.
Marth's kill moves are d-smash, upsmash, f-smash, uptilt (at high percents), uair (at high percents), nair, bair, and up B. Uair, bair, and Nair are kinda pathetic if you don't tip them though.
You left out dair. Fair or nair -> dair is a legit combo. Although it's probably safer and overall more practical to kill with if you were to just combo into reverse upB in the situations you would spike, except at very low percents (although even then, with the angle it sends at, reverse upB can still set up for a nice edgeguard).
I'd also like to emphasize dsmash here, since the move is faster than fsmash and kills about as early as fsmash does, while sneaking under shields and punishing people that try to roll behind you, but at the cost of some range, being harder to tip, and being
much more punishable if you miss (over 40 frames of lag from the
second swing, with almost a full second of lag from the first). The move is safe at any percent on hit as long as you tip it, and I'm pretty sure it's safe on hit even if you don't tip it starting in the early 20s or so (possibly sooner), and seeing as it puts them up into the air, I've actually found myself using it across a wide range of percents to either set up juggles or for killing. Interestingly, if you hilt it, the move has a very cruel angle that will set up for edgeguards, making the middle of the blade the least useful part.
Anyway, as for kaiser... Marth has some really mean edgeguard options against ness. If he's forced to upB, marth can just counter it, turning ness's good old nuclear warhead back on him, and forcing an upB is often as simple as just swatting him away with aerials (tipped bair, nontipped fair, and either tipped or untipped nair, although obviously tipped is more effective). And of course, since ness has to just sit there for a while while he's aiming his upB, marth also has a
very easy reverse upB kill on him if he's willing to risk going down there. This is of course in addition to everything DS just said.