[Oversway]

I've read that Frozen Heart does NOT check cold resistance, but I havn't tried it myself.

On the other hand, I've never heard of astral weapon not working. Especially with one class of monsters. I'm not that suprised it doesn't work with trample, however.

I'd still have a go at the ID with your nat again. If you were going for the high def ID with luck, missing all those times could be possible.

If still no luck, you could try a couple other weapons to test the theory. The armor negating dagger (I think its 1s1d) might help. A higher attack weapon - fire sword or better yet firebrand might also help you hit.