To start off, why would you ever agree on going to FoD against Peach with Falco, while you can stage strike >_>?
I'll edit in more later about the Fox matches
You remind me of me, we have the right idea, but are too impatient and dumb and get wrecked for it. For example on Pokemon Stadium with the fire transformation, you approached her on the left side for no reason. That was a very bad idea.
Something you should really give a try is shining while you're in the air. Coming in from above with just a shine on her head at 45 degrees angle, you can jump away again (best if you have a platform to go to). It sounds dumb to just do 4 damage with a shine, but if it hits, it sets up for a lot of things. It works very well, somehow.
Dashdance more when you're both in neutral positions. Sometimes you can bait a dumb dash attack and punish with U-smash OoS or whatever you like.
You are making it so much harder on yourself by not using lasers. Those mother****ers rack up damage, per match I'd say 50 lasers hit, easily, for 100%, that's a whole stock you can laser away without camping hard. Don't do like 3-4 SHDL's in a row, but just throw in one while retreating, then come back in and dash dance a bit. Do it again if she doesn't approach.
After they fair your shield, there's nothing you can do that is a good option, except rolling away. Jump out, get jabbed, grab, get jabbed, roll behind her, eat dsmash, stay in shield, get poked by dsmash. So roll back after F-air if you can, you should be fast enough.
Oh and a tip in general, useful for any character: Get Shine OoS down. If you can do that, your life will improve.
Vs Nintendude I didn't see much of what you were doing wrong, because you just outplayed him. He didn't punish stuff he should've etc.