Obviously you need to learn to buffer dashes out of grab releases on MK. If you have absolutely no MK to practice with, you can try wifi. Wifi helps with MUs you don't get to practice offline. The MK MU definitely takes a while to learn.
You need to react better. It's really important to have a good reaction time against Meta Knight. Mix it up better from the ledge. All you did was ledge jump and ledge hop. Marth's has the best regular get up from below 100 %. It's invincible from frames 1-30 and ends on frame 32, instead of the average being vulnerable for 4-5 frames.
Don't let yourself get cornered. If you're close to the edge, then the chances of getting offstage is much larger, which is bad against Meta Knight. So try to get to the center of the stage and corner MK himself. We can pressure MK very hard when we manage to corner him and force him to the ledge.
You need to space better your Fairs. As hard training as it requires, being close to perfect with your spaced Fairs is a must, as that changes them from being very punishable to close to unpunishable.
@ 0:42 you missed a crucial punishment and instead you rolled to the edge and got yourself gimped. Also, due to us being invincible from frame 1 during Up b you should up b if the opponents goes into your height during Up b.
@ 1:00 you should have just regular get up cause he was too far away to hit you out of that option and instead you ledge hopped and got punished for it.
@ 1:40 after killing the MK you should have IMMEDIATELY have left the ledge. You don't want to be there, especially not against him.
I'm too lazy to watch everything.
Because MK is such a hard MU to learn, I suggest you to go and read as many MU guides about the Marth MK MU as possible. There are some really good guides, like this
http://www.smashboards.com/showthread.php?t=203056