Question about Sunder + Conviction

A couple of weeks ago I got back into D2R after a long break (I stopped playing before they launched the ladder), so the concept of Sunder charms is still pretty new to me.

I'm making a pvm FoH Paladin. He's currently wearing a -19% / +15%

Griffon's Eye and a level 33 permanent

Conviction aura. Now I'm wondering if I somehow bottleneck myself by putting a

Crack of the Heavens in his inventory, because of the mechanics I read about it. It says

• If a monster is Immune to Fire, the Sunder Charm
  Flame Rift changes its Fire Resistance value to 95% which means it is no longer Immune.

• Lower Resist,
  Conviction and
  Cold Mastery apply for 1/5 of their values after a monster is sundered.

• Any other -x% Enemy Resistance source is 100% effective.

So since

Conviction already breaks the immunity, is it even worth it to have the enemies' resistance at -5% base value just to nerf my

Conviction level by 1/5?

Sorry if I'm being dumb lol

You have to remember that

Conviction works at 1/5 effect when breaking an immunity regardless if you have a sunder charm or not.

Conviction only works at full effect if the enemy was not immune to begin with.

Say an enemy has 100% Lightning Resistance (lowest possible to be immune).

• Without
  Crack of the Heavens, your
  Conviction would break the immunity. It would work at 1/5 effect while breaking the immunity. A level 33
  Conviction applies -150% to enemy resistances, but at 1/5 effect that's -30%. Add the -19% from your
  Griffon's Eye and the enemy will end up with 51% Lightning Resistance.
• If you equip the
  Crack of the Heavens, the sunder effect sets the enemy to 95% Lightning Resistance.
  Conviction then again works at 1/5 effect (-30%) and coupled with the -19% from
  Griffon's Eye, the enemy would end up with 46% Lightning Resistance.

Now, take an enemy with higher resistance instead, say 115%.

• Without
  Crack of the Heavens, you'd still break the immunity, but since
  Conviction still only works at 1/5 effect while breaking an immunity, the enemy would have 66% Lightning Resistance in the end.
• With
  Crack of the Heavens you get the exact same result as if the enemy had 100% Lightning Resistance to begin with - they have 46% in the end.

In fact, even if the enemy has 200% Lightning Resistance (possible with some unique monster modifiers), the end result would still be that they'd have 46% Lightning Resistance in the end if you have

Crack of the Heavens in your inventory.

Conversely, the maximum immunity you can break with a level 33

Conviction is 129%. That would leave them att 99% (before

Griffon's Eye or other effects with -res).

Conviction caps at -150 at lvl25

Pierce from facets/gear works normally

so i think yes... respec and limit

Conviction to 25 and usr those points elsewhere

Those were incredibly helpful answers. Now it makes a lot more sense.
Thanks @ShadowHeart @krathkor