Diablo 1 HD Hellfire Mod | Awake

Have a few questions about items that have "Chance to cast X on striking":

1. What level is the spell being cast? Is it tied to the level of that particular spell your character has in the spellbook?

2. I found a unique low level staff that has "CtC Frost Shard on striking" and from my observations some spells I cast do indeed trigger frost shards. However, while using Chain Lightning I do not notice the thing triggering. Are only some spells capable of "striking" mechanic or are my observations wrong? Is there a list of which spells work and which do not with it?

3. The other thing I noticed is that sometimes Frost Shard triggers BEFORE my spell (Charged Bolt, for instance) hits anything, at least it looks like it. Seems it might be coded more like "CtC X on spellcast"?

4. Is there a hidden cooldown on the CtC trigger?

2) I think it really works on striking (when you autoattack target), not on spellcast. Exceptions are some spells like Blizzard and Meteor Cluster, which at the same time with casting the spell trigger an autoattack.

1. Yes.
2. I think the spells that multihit don't proc on striking, maybe at all or just less often.
3. Yes it's cast, you don't have to actually hit a target for the proc to happen.
4. No cooldown, just the chance, consecutive casts can trigger it each time or not at all.

Playing Barb I found that is is in not possible to use such good armor as Stoneskin because of lighting enchanted bosses.
The Armor has "2% Chance to Cast Stone Curse When Struck" but, I believe, every each charged bold (emitted by the monster on every hit) took part in the calculation. So hundreds of sparks multiplied by 2% chance always turned the monster into the stone in just 1-2 seconds. In the stone form monster gets very high resistance to physical attacks - means, you damage him much less, you litch much less but still get full damage from lightning sparks, so you die fast.

From another side, Glory (Unique Ward) helps a lot in the same scenario, because of "2% Chance to Cast Healing When Struck" and "3% Chance to Cast Nova When Struck". So my Barb spawning Novas and healing himself in crazy way. Now I am trying to max these spells to make them work even more effective.