I am writing this as a quick reference resource for people interested in the Stalwart Defender III PrE. Please let me know if any of this should be corrected.
* Please note*(in brackets are the limiter for the max dex)
Also the total ac gain is from just the Armour/Shield/Dex, no rituals, DT runes or magical properties .. this is strictly the total ac gain from the base gear itself.
DT FP and Tower for non dwarf .... MDB of 6 or shooting for 22 dex
(1 DT + 2 PrE + 3 FAM = 6) ... total ac gain 30 (15 DT + 9 TS + 6 Dex = 30)
DT FP and Tower for dwarf .... MDB of 8 or shooting for 26 dex
(2 Tower + 3 PrE + 3 FSM = 8) ... total ac gain 32 (15 DT + 9 TS + 8 Dex = 32)
DT FP and Mith Tower for non dwarf .... MDB of 6 or shooting for 22 dex
(1 DT + 2 PrE +3 FAM = 6) ... total ac gain 30 (15 DT + 9 TS + 6 Dex = 30)
DT FP and Mith Tower for dwarf .... MDB of 9 or shooting for 28 dex
(1 DT + 2 PrE + 3 FAM + 3 DAM = 9) ... total ac gain 33 (15 DT + 9 TS + 9 Dex = 33)
MFP and Tower for non dwarf .... MDB of 7 or shooting for 24 dex
(3 MFP + 1 PrE + 3 FAM = 7) ... total ac gain 29 (13 MFP + 9 TS + 7 Dex = 29)
MFP and Tower for dwarf .... MDB of 8 or shooting for 26 dex
(2 Tower + 3 PrE + 3 FSM = 8) ... total ac gain 30 (13 MFP + 9 TS + 8 Dex = 30)
MFP and Mith Tower for non dwarf .... MDB of 7 or shooting for 26 dex
(3 MFP + 1 PrE + 3 FAM = 7) ... total ac gain 29 (13 MFP + 9 TS + 7 Dex = 29)
MFP and Mith Tower for dwarf .... MDB of 10 or shooting for 30 dex
(3 MFP + 1 PrE + 3 FAM + 3 DAM = 10 for MFP)
(4 MTS + 3 PrE + 3 FSM = 10 for MTS) ... total ac gain 32 ... (13 MFP + 9 TS + 10 Dex = 32)
Also for reference: Stalwart Defender III
+3 Max Dex Bonus to Tower Shields
+2 Max Dex Bonus to Heavy Armour
+1 Max Dex Bonus to Med Armour
This information should make it much easier to use as reference for what dex you want to aim for with current information. I will update this if any new items come out to change this base breakdown.