When I talk to Esbarn, he doesn't say anything, and the subtitles wizz by in moments. I can choose a response, but even when I finally guess at what Esbarn's been saying(cause of the speed at which the subtitles are replaced or removed), the old man doesn't open the door. I can not continue until that old crazy man opens the damned door.

I've had this problem before, what you have to do is download the sound file of Esbern's dialogue, extract it and place it in Skyrim's data folder.
You can download the file here http://www.filesonic.com/file/3510536384/sound.rar

Much obliged, good sir.

One follow up question; will this audio fix allow me to continue the quest, ie, once he speaks normally, will he open the bloody door?