Regarding Falcon, IIRC, Uair should also work in the same way as above, In fact, Uair can get you out of a lot of situations when facing Falcon, due to the fact that it's technically his fastest aerial, and it comes out in front of Marth, as opposed to just above him (Fair).
Of course Dolphin Slash would work due to the invincibility frames it grants, but if you have no safe place to land, you are probably going to die after you land to a powerful Smash, or even the Knee again. This is probably one of the better options on stages like Dreamland and Battlefield, as you can land on one of the platforms easier. Plus, with all the areas to land, it can become a guessing game for Falcon, especially if you are very close to the ledge of one of the lower platforms. Will you land on the edge, or will you go just to the side of it and land on the floor? It's a niche thing you can remember on Smashville and Town and City. NEVER do this on FD. You WILL be punished.
But in general, Fair or Uair with away DI like mentioned above is probably the best option. I too, have a similar experience with an extremely good local Falcon. The first time we played, I used Rosalina the first game, and Marth the next, but got swiftly 2-0'd. The second time we played, I actually swiftly 2-0'd him with Marth (this was the first time using 1.1.4 in tournament [the end was super awesome; my sour Fsmash somehow clashed with his Falcon Kick, andI then finished with a tipper Fsmash). Now, we tend to have really close games; it's a really good friendly rivalry we have going on. I tend to use Marth against his Falcon now, even over Rosalina and Bayonetta, and I win most of our encounters (he also uses Mario, so that's not really a great option to counter Marth, you see). I just seem to play much better in that matchup with him than the others. Jab is such a fantastic tool in general, but it's really helpful here, I feel. It's relatively easy to zone Falcon out with defensive play.
Could just be that I have decent experience in the matchup, but I never get why people seem to think Falcon beats Marth. Is this still the case? If so, why?