1)Bad stages:GHZ,Metal Cavern,FOD i guess, and Lyalt Cruise now that's probably the worst of them all.
2)Fox dosnt really have a bad Match up and its definitely not Zelda lol.
3)Just try to get in with attacks and use your movement or you can just laser camp. Make sure to go on youtube and type Fox vs marth or Fox vs Link.
1) GHZ and FoD are fine for Fox. The only people he wouldn't want to end up on MC against would be characters with strong recoveries and bigger characters that own the stage, like Bowser, DK, or Dedede. Dedede also has the amazing recovery, so that's double bad, but he's kinda bad so it probably all evens out. Lylat cruise is only bad on account of the ledges, which just make it more difficult, not necessarily worse. His only other "bad" (or "meh" stage as he can function anywhere) is Dreamland.
2) I would agree he doesn't have trouble with Zelda, it's just a pain in the ass. I went to check the Fox matchup spreads for Melee's top tier characters, but the guide didn't have ratios for me to just look at. I know he has a little trouble with Falco, and possibly Marth. Main thing is that any character can punish Fox really hard if he leaves himself open, so you have to be extremely careful against basically everyone.
3) This is good advice. If you don't mind playing lame, just laser camp and force them to come to you, which in the case of Link or Samus, as examples, will already put them in a bad position since they're not built to approach.