I'm listening to your Issac video right now...
You need to be confident in the way you speak. You need to learn how to control your breathing, but that comes with confidence. Right now I'm hearing you taking huge breaths in the middle of sentences, and in normal conversation we don't do that. You need to talk in a similar fashion to how you just talk normally. I know it is hard, but it is possible. Imagine your not LPing anything, you are just showing the game to a close friend.
On that note, you might want to cut down on gimmicky phrases that make you sound like a game show host. Watch somebody like NorthernLion who is hopeless about the game, but gets by on his natural charisma. At no point does he sound like he is addressing an audience, instead he is talking to a friend.
Also, it is better to take damage because you were distracted by talking, than have silent spots. Narrate what ever is happening on screen. When you get a chest say that you are going to grab that chest. I should be able to tell exactly what is going on without actually looking at the window. With more popular LPers I can have their video in the background and know exactly what is going on, but right now the only reason I even know you just beat a boss is because of the music. You have to assume I am freaking blind and tell me what I am looking at.
Just playing isn't enough unless you are so fucking pro that the gameplay itself is impressive, and then you don't want any commentary at all. What you say is more important than how you play. It sounds like you are fighting wrath right now because of the bombs going off. I really don't know. TALK TO ME DAMMIT!
On the plus side, as things went on your vocal patterns got more natural. Breathing is getting a lot better. You need to be more casual about the intro I guess, but the thing you really, really need to do is talk to me! A boss just died and I don't know what item you picked up or what it does. Fix that! Your saying 'This may very well kill me', well what may? It might feel silly to narrate the entire game, but you have to!