From what I've heard on this forum, the "get all the strongholds" mod is pretty buggy.
To quote from Duncan Clay's wonderful BG2 walkthrough:
(it's spoilerific!)
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To get all 8 strongholds you must do the following:
1. When talking to the person who gives the stronghold quest, and when
talking to the person who ends the quest, use Shadow Keeper to give
yourself the appropriate class.
2. After getting each stronghold, you must set the stronghold flag back
to zero by typing the following into the debug console:
CLUAConsole:SetGlobal("PlayerHasStronghold","GLOBAL",0)
(And in case you're wondering, the link to the walkthrough
http://db.gamefaqs.com/computer/dosw...rs_gate_ii.txt