Yes, you can dual class in your situation later in the game, since you have high enough STR and INT. As any other fighter should, the DEX should be 18, same as CON. With that said, the only 2 remaining stats is WIS and CHR. Personally I am one of those ppl who sit in front and continuously roll dices to get at least 93 totals, I would put at least 10 on WIS and the rest to CHR.
As for weapons, I usually dual wield Crom Faeyr in off hand, and Daystar/Celestial Fury in main hand. Meaning proficiencies will be in 2 weapon style (set to 3 slots), the rest will be mainly on hammers, and the remaining split between long sword and katana. I usually have more on Katana since I only use Daystar for its "sunray".
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Long live H22A1!!!!!