I believe it should be Precor parumper curatio bona pro James Xavier.
I don't think so. For one thing, James is just the English form of Jacobus. For another, names in Latin are treated just like common nouns so that even if James was accepted as correct, the noun endings would not retain the 'James Xaver' form. Also, although precor
does mean to beseech or to pray for, I'm not sure you've got the declension right.