How do you do that with the capture card and still have audio? Or is it just a really good camera?
At lower percentages, you really should focus more on techchasing if you're going to dthrow instead of aerial combos. Your approaches are also a little too direct. You basically charge across the stage with an attack, and a better Marth would intercept and punish you for each one of them. Marth's greatest strength is his priority and you need to find an opening before you rush him because you're not going to out prioritize him.
You're using your second jump too much. If you get hit out of that (which can and will happen against Marth) you're going to be stuck with Falcon Dive against Marth's edgeguarding. Not fun. Trust me on this one. Speaking of recovery, recover lower.
Also, you're looking for the kill too early. You're not going to knee Marth to death at twenty percent. You need to know your kill ranges for different percentages. Depending on percent, positioning and edgeguarding, this can be between sixty or a hundred, I'd guess.
Your comboing looks a little... tentative, I think is the best word to describe it. Don't be scared of him. Pursue aggressively in your combo. The more aggressive you are, the more defensive they'll be and that's what you want. Also, more experience helps you learn spacing and follow ups and such.
Just in general, move around more, be more aggressive and you should be okay.
