I used to play Marth without the C-stick before I saw the light. To L-cancel like that, you have to jump, do your aerial, then either let the joystick return to its neutral position and fast fall L-cancel, of you can roll it into the down position and L-cancel. Just remember that his L-cancel timing is a little weird compared to other characters. Chain-Ace did a good job of explaining it.
As for a double retreating Fair, it's just not gonna happen. I actually just went and tried this because I have nothing better to do at 2:40 in the morning. The succession of the Fairs is very precise, so trying to input a back command between two precisely timed Fairs would not only be difficult, it would have very little "retreating" effect. You could try to short hop backwards and then do it, but not only could you do a Bair instead, any backwards movement gained from the backwards short hop would be negated by the forward input of the Fairs. The best I could get in .25x speed in training mode was a SHDF out of a dash that only moved forward a little, and a backwards SHDF out of a dash that moved back off the short hop, but moved forward to the same position during the Fairs. That's the absolute best you're going to get, and at regular speed would be unnoticeable.
Contrarily, a non-retreating SHDF is very easy without the C-stick, but don't be under the impression that its the most important thing. Read this for more info:
http://www.smashboards.com/showthread.php?t=265312
Short hop Uair isn't too hard, just make sure to not tilt your joystick all the way up when you do it. Its the same as using a Utilt when on the ground.
*sigh* He has a baby hand, that's why he can't use the c-stick dammit!!! He was seriously saying he simply cannot use the c-stick.
Assuming that means what it sounds like, I still don't think a JC grab would be too hard to do with Y+Z. I was kinda thinking you could play claw, but I really have no idea.
Pleeze help ( also I can't use the c-stick) 
