Sage:
I would, at lower percents, recommend dthrowing Marth, as opposed to fthrowing him. From a down throw, you can at least get a dash attack, while fthrows don't get you much.
Roll a bit less. I say a bit, because you had some rolls where you rolled into him and then got to do other things, but the Marth quickly caught on, and started looking for them. Rolling towards your opponent is genrally bad, too.
It's good that you got a lot of grabs on him. Just cut down your rolling, and use turnips as a baiting tool more (they way you used them is good, but they are for more than just approaches).
???? I guess he goes Luigi on KJ64 cause it's easier for him against Peach than being Marth on KJ? Or is it simply that Marth is fairly bad there? I dunno. You just look unfamiliar with the Luigi MU, and Vanz has information on that. I don't think that the way you were camping him was really putting pressure on him, which is important in that MU. You just kinda chucked turnips at him. Also, Luigi's shield pressure should be respected (to a degree). Remember to be patient if he's already pressuring your shield, or just avoid being in it more than you have to.
I hope that kinda helps. I'm not sure about specifics on handling what he does to shields, but perhaps someone else is...?