Few more ways beside what you said:
-glide attack then up b (be care ful to space well, so you don't get shieldgrabbed...
-side b
-side b
-side b
-side b
-drill rush
-side b.
that's the best way to recover...
You forgot triple dash... Therefore that's only the "second best way" to recover. Anyway, back to business...
So it's mostly against projectile attacks huh? Well for King DeDeDe, 1 thing you can do is just air dodge his projectile and stay low when approaching the edge. Once you think you are about parallel to the edge, ^B and grab the edge. If it didn't hit the opponent but you grabbed the edge, do what I told you to do in my earlier post when it comes to getting past your opponent. If you don't think that you've got enough jumps to do that, try to >B towards the ledge. As you move foward, it should swat the waddle dees away in the process. Watch out for Gordo's though, (Sea Urchin looking ones.) they're invincible. It's the luck of the draw on that one...
For Falco, stay low and air dodge the first set of lasers. Be wary however when you approach the stage. Falco may jump off and try to spike you with his Dair. Meteor canceling won't work too well here. I suggest you air dodge that too.
For both Link's, (I know you said T.Link, but IMO, both work in pretty much the same trend.) I think their projectiles are quite easy to air dodge. The only one that can be remotely controlled are their bombs, but I think these are fairly predictable too. Could just air dodge them too I suppose.
The 1 solution for all characters is that you can glide underneath the stage (Only if it's possible!) and grab the edge on the other side of the stage as thatsyournamedude mentioned earlier. Although if up against either Link or T.Link, (Or anyone else who has a pick-up projectile like their bombs.) I probably wouldn't glide under the stage because if the bomb hits you, they can use their Dair to hit you while you're in hitlag (Whatever it's called.) and may KO you depending on your %. Don't know if their Dair's spike you though.
Also for that 3rd question I asked, I wouldn't recommend using the ^B just to attack the enemy. Use it as a quick ledge grabber. Also, if an enemy tries to attack you during your ^B as you attempt to grab the ledge, it won't work for 2 reasons: They'll get hit by the attack if they were too slow to attack you beforehand. Second reason is that if they attack you and you've just initiated the attack before the hitbox comes out from the enemy's attack, you'll hit them because of the invincibility frames that occur at the start of attack. Therefore, you can't get hurt/be interrupted when you start the shuttle loop. (I think I may have said it the wrong way. However, you are invincible when MK initiates the shuttle loop. So reason 2 still applies.)
Lastly, do they use these projectiles in a certain way or do they just spam it hoping that they'll hit you? Let me know if this didn't help. Its been a while since I have been put into situation like this.