Did some rough tests on the SC damage with the shield
Lv1 skillchain:
Target: Locus Camelopard (resistance ranks: Fire 130%, Stone 100%)
Gear: Joyeuse + Diamond Aspis + normal TP set, also for the WS (without SC damages or affinity bonus during WS)
Day: Stone
Both the target and the day were not ideal, but for a rough test it seems some insight can still be gained
1. RLB: Damage 3230
2. Seraph: Damage 1603, SC (scission) damage 984
3. RLB: Damage 1262, SC (liquidation) damage 784
4. Seraph: Damage 881, SC (scission) damage 616
5. RLB: Damage 1428, SC (liquidation) damage 1481
6. Seraph: Damage 1287, SC (scission) damage 1158
7. RLB: Damage 313, SC (liquidation) damage 406
8. Seraph: Damage 474, SC (scission) damage 474
9. RLB: Damage 1204, SC (liquidation) damage 1721
10. Seraph: Damage 399, SC (scission) damage 399
11. RLB: Damage 338, SC (liquidation) damage 439
12. Seraph: Damage 642, SC (scission) damage 642
13. RLB: Damage 1641, SC (liquidation) damage 2133
14. Seraph: Damage 1603, SC (scission) damage 1603
Extrapolating from the SC damage table (0.9 at 6 steps), it appears that the multiplier caps at 1.0 from the 7th step onwards.
LV2/3 skillchain
Exacalibur + Diamond Aspis + TP set
Target: Locus armet beetle (BG wiki says it has 100% resistance rank across elements, but it appears that it has 150% on light and ice like any other beetles)
Day: stone
1. Savage: Damage 4164
2. CDC: Damage 2518, SC (Distortion) damage 2544
3. KOR: Damage 3203, SC (Fusion) damage 3882
4. Requiescat: Damage 1502, SC (Gravitation) damage 1856
5. Savage: Damage 4724, SC (Fragmentation) damage 6091
6. CDC: Damage 3563, SC (Distortion) damage 8295
7. KOR: Damage 2625, SC (Fusion) damage 7168
8. Requiescat: Damage 1496, SC (Gravitation) damage 2804
9. Savage: Damage 3181, SC (Fragmentation) damage 5782
10. CDC: Damage 4562, SC (Distortion) damage 12253
11. KOR: Damage 2129, SC (Fusion) damage 5866
12. Requiescat: Damage 1708, SC (Gravitation) damage 3125
13. Savage: Damage 4834, SC (Fragmentation) damage 5752
14. CDC: Damage 4562, SC (Distortion) damage 18490
15. KOR: Damage 2332, SC (Fusion) damage 6400
16. Savage: Damage 4336, SC (Light) damage 16539
17. KOR: Damage 3407, SC (Light) damage 13054
Based on the apparent resistance rank 150% on Ice and Light, it appears that also for LV2 and LV3, the multiplier caps at the 7th onwards. Extrapolating from the known table, it appears that the multiplier for LV2 caps at 1.75 (or 1.8) while LV3 caps at 2.5