Please help figure out this build

Hello

Disclaimer: I'm trying to follow CATPOST's Boneshatter Jugg build for H SSF R https://poe.ninja/challengehcssfr/builds/char/catpost/CATPOST?i=1&search=sort%3Ddps

Can someone have a look at my character SnucSSF and help me figure out the following:

1.- Why is molten shell not being triggered by CWDT and only Vulnerability is getting triggered. Note: I have additional vulnerability/molten shell in my second weapon set because I bought new ones thinking it was due to a gem level thing, but MS won't trigger even using lvl1 gems

2.- Is this build not using Determination? When paired with arrogance, determination's reservation cost goes up to 105% which will make it impossible to activate... Am I missing something here? I'll drop Arrogance for the time being.

3.- What should I give more priority on my gear's stats? (after sockets of course) the build is using a combination of armor and evasion but I'm finding hard to find the pieces with right stats and sockets/links combination

Thanks in advance for any help.

Note: I'm running Sanctum SSF as learning experience, but my goal is to move to HC SSF and to level directly without using neither refunds nor league starters... and reach as high as I can in maps and bosses

1 - molten shell probably to high for cwdt.decrease it's lvl by vendor. 1 lvl cwdt + 8lvl molten shell

2 - on poeninja he is using determitation. for mana reserv for this skill-near blood magic armoury mastery with mana reservation efficiency

3 - armour/evasion