Not quite right as by default xbows do not have dex to damage natively (unlike bows) they do have dex to hit natively though.
It is worth noting you can only have one stat to damage though so if there are multiple sources (eg via fvs or feydark) only highest applies
Are you sure? I haven't done a ranged build in a long time but I thought they had changed all ranged weapons to have dex to damage by default.
Anyway, it's worth noting that while insightful damage works, you'll still use dex to hit unless you pick the relevant enhancement from harper agent (you can't have both insightful damage and insightful attack active at the same time, they're both weapon enchantment) and make sure to pick the int trance know the angles at the same time.