@xiamumomo Let me try to answer each issue:
<OffhandAdjust: x> This changes the default stats of the weapon by x% ONLY when it is in the offhand. (Equip slot 1 by default. Equip slots are numbered 0 through 4)
<PotentialP: Number> just adds a value for use when using the auto equip command from the menu and can be omitted.
<mainweaponTrait: x, y, z>
<subweaponTrait: x, y, z>
<doubleGripTrait: x, y, z>
These all work properly when I tested them in a vanilla project.
What I did notice is that your uses all added extra spaces which WILL make them NOTwork.
I'm not sure how you can go about fixing it, but maybe a screenshot or video might illuminate what you are doing wrong here.
So if you wish to do that, go right ahead.
Finally, <monkeygrip> (not < monkeygrip > with the spaces) will allow the player character to equip a shield with a weapon that has the <twohand> tag.
Normally the <twohand> tag will prevent equipping anything else to the other weapon slot.