Can someone explain these to me a little bit? I seem to be finding conflicting or non-concrete answers.

1. If I get a sunder charm on a cold sorc. Will I be able to do damage to enemies that are cold immune? Do I need to have a certain amount of points into cold mastery in conjunction with the charm or is the charm enough to break?

2. I am seeing a little fluctuation on pricing and stats on the trade forum. What are the min-max stats of a sunder charm? Which ones are more valuable -70, -80 or -85 etc.? 85 theoretically offers more penetration but the 70's are selling for more with the trades I have noticed.

For sake of ease, we can use a cold sunder charm for my questions above (I understand physical res one has different numbers). Any info would be greatly appreciated.

1. yes, you will dmg cold immune. yes, you need a lot of cold mastery. the charm just removes the immunity, thus the previously cold immune monster has now -95%

2. -70 to -90. no, you misunderstood this completely, this affects you. that minus res is on you.