Okay I shall attempt to answer all these these questions to the best of my knowledge. Starting from the top.
- Pichu being tiny, yellow, and considered by most, the worst character in melee is what the fook is up with this character
-Pichu vs Fox= hard, so i wish you good luck
-If you know hes going for the edge, ftilt would be the safe bet, fsmash if you're ballsy
-there is no real gimp pichu has so best bet if they're below you is to dair them while they're charging upb
-uthrow to most attacks work at lower percents like fsmash usmash, dthrow tech chasing can work pretty consistently if you can predict your opponent and if they miss the tech you can jab reset into another grab or usmash, just experiment with the grab game since there is a buncha stuff you can do.
-Yes it is a rather horrid move, should almost always be replaced with a dtilt or shffled aerial.
-You don't see Pichu winning any races so yes he has a horrid dash, you could try lag canceled up-bing, but there is a heated discussion about it in another thread here so do what you must ;D
-Pichu has a nifty dsmash, sorta like Docs dtilt but stronger
-I believe his uair has a hard time getting CC'd maybe at <10% but shouldn't anytime after
-You can Usmash out of shield, wavedash OoS to get closer, or shieldgrab, all works
-Depends how high fox goes, if he doesnt get to the point where he doesnt touch near the part where it has to zoom in then probably not, maybe instead using uairs to try and get more comboing in, if he does get a bit of height, there is nothing wrong with getting that few extra percent and maybe that kill if they don't DI
-On the ground ftilt, in the air Dair, both have priorities higher then most moves