"would proclaim" or "were to proclaim." This is describing something that has not happened and should not happen. (See: [[rc://en/ta/man/translate/figs-hypo]])
## other than the one ##
"different from the gospel" or "different from the message"
## he should be cursed ##
"God should punish that person who preached a false gospel forever" (see UDB). If your language has a common way of calling a curse down on someone, you should use that.
## For do I now want the approval of men or God? Or am I seeking to please men? ##
These rhetorical questions expect the answer "No." AT: "I do not seek the approval of men but instead I seek the approval of God. I am not seeking to please men." (See: [[rc://en/ta/man/translate/figs-rquestion]])
Both the "if" phrase and the "then" phrase are contrary to fact. AT: "I am not still trying to please men; I am a servant of Christ" or "If I were still trying to please men, then I would not be a servant of Christ."