Haha, that's the song for G-reg's combo video. Confusing me, man. For one, you should be playing four stock, and starting as Sheik =P
Don't just stand there, especially against Falcon. Move around, wavedash, dashdance, throw needles, whatever, just don't just stand there.
Also, don't roll so much... and it's probably a good idea to stay grounded for the most part. Sheik's shffl game is a bit lacking, and you'll be in the air for a while, so Falcon could bait a nair, then grab you at the end. And you don't want to get grabbed by Falcon.
Don't ledgejump. Ledgehop an attack, ledgedash, or ledgestand if you must, just don't ledgejump. And jump cancel your grabs.
I wouldn't bank on Falcon missing techs. Just dthrow and techchase! If he hits the ground and doesn't tech, then jab him for the tap reset.
Uthrow is a bad idea.
Fsmash, also a bad idea.
I'd work on the approach. Needle cancel or something. Fulljump nairs aren't really a good idea. If you really want to be lame, just wait for Falcon to try to appraoch you and ftilt him.
You have a lot of idle time. Just... move around, do something to occupy yourself. Be a threat.
Remember, you can airdodge back onto the stage too.