The inner joint can be a PITB, but you are going about it the right way. Here's an image of what it looks like in the splined side of the inner:

On the end of it, there's the small ring. It is what holds the axle securely in place. To get it out, is just a matter of applying the right amount of pressure in the right direction. The ring has to compress, and the axle comes out. I can tell you don't be afraid to apply some force, because it will take some. A prybar is usually your best bet. You just need to find the leverage point between the two parts (like wedging it off of one of the protruding bolts) so as to get the ring collapsed.