I have some small optimization suggestions and some preferences and updates.
-I think you're overestimating the impact of max mana %. It only boosts mana from hard points in Energy and flat mana. You also stack so much of it, that Chams struggle to ever beat Zol or good jewels. I was playing with a spreadsheet theorycrating an endgame setup and even with full UMOs, 2% max mana is roughly equivalent to 2% energy, 5 flat energy, and 25 flat mana (and that's putting aside awesome 3 or 4 roll jewels that have flat life and other stats on top of that). It's worth investing in crafting jewels. Can even go all res recipe to help with Labbing resists as needed. Belial Trophy is miles better than Yshari for the same reason and I think second trophy is better as bremm for avoid stacking.
-Others have mentioned but 2 points for crystalline barrier is definitely worth it. Especially lategame, you can get a ton of prebuffing spell damage for free from fire dance, blood fury, and bloodlust. Can cap the flat damage reduction with just prebuffs and free spell damage from charms and incidental bits on gear (adding MotW from relic/mastercraft gloves with the strength enhancing items). The 200 flat PDR/MDR works very well with mana shield.
-Raven Familiar is better than specialization. Same effect on your nukes and you get free levels for oskills/Living Flame/spell damage buffs for Crystalline barrier prebuff. You're probably better off with a different third mastery after Meditation and Continuity depending on content and level.
-Vaetia's Wall is just worse than Starlight. Good flat mana on starlight is more important than a little more max mana and space for Chams (see above). Also, max res Pgems are less costly than the difference. This is also putting aside the orange text, 2 all skill, and high +totals to your nukes. I think Warp Armor/Living Flame is a better coven pair. Starlight gives equivalent regen while dumping mana for immersion to a soft point living flame. Avoid stacking is good for the build too, BIS items give you 20 avoid to start with. It's like 24% less all damage types versus less than 33% less physical damage if you just leave phys res at the 25% you get for free with Starlight and other obvious choices. Resistance applies after flat damage reduction while mana shield applies before it, so the benefit of capped phys is not as big on Sorcs generally and less so on cold/mana.
-Last is Angelics for boots and belt, but guide was written before them. 3 skills, 150-170 flat mana then other gravy stats and space for 3 spiritual blessings. Much better than the old options.