GOOD STUFF.
Those friendlies with Bwett were just GOOD.
The only thing I'll address is your concern of lacking a reliable kill method.
My opinion: Yeah, but so what.
It may be a lack of skill on my part, but I often have opponents (ESPECIALLY my friend who mains a Yoshi almost as good as Bwett's) who live to 200%. It often happens inconsistantly, and it only rarely happens against non-Yoshi's. Because of that, I would say just deal with it and keep chaingrabbing.
In Bwett's first stock in the second video, he lived to 250% instead of just 210% because of your desire to get a kill asap. You F- and B-threw him repeatedly when it wasn't going to kill him. Obviously it added damage, but it would have been preferable to try to chaingrab him to the edge of the stage, which would have added much more damage and less distance for him to travel to death.
[unconfirmed preaching]
Against Yoshi, the ONLY thing you can get him with somewhat reliably, in my experience, is the grab. ALL of your other attacks only hit him if he makes a mistake, or if they were a part of a combo-thing. Because of that, I only use the attacks to space, just as if he were at 0%.
[/unconfirmed preaching]
Main point: Don't waste a grab agains Yoshi (or any character), and don't start spamming Dash attack trying to get a kill.
I'm actually going to get to play against my friend's Yoshi tomorrow, so maaaybe I'll have links to videos for you. They will be worse than yours, and they won't do crap to show what I just said, but they'll be there. Within the next year. :O
I definately agree with
Even if you play the same characters you normally play against, they will be different when used by different people. It's great.