As for taking cues from those who elected him, you might want to consult Edmund Burke's Speech to the Electors of Bristol. A salient quotation from it:
"Parliament is not a congress of ambassadors from different and hostile interests; which interests each must maintain, as an agent and advocate, against other agents and advocates; but parliament is a deliberative assembly of one nation, with one interest, that of the whole; where, not local purposes, not local prejudices ought to guide, but the general good, resulting from the general reason of the whole. You choose a member indeed; but when you have chosen him, he is not a member of Bristol, but he is a member of parliament." And further: "Your representative owes you, not his industry only, but his judgment; and he betrays instead of serving you if he sacrifices it to your opinion." (Speech to the Electors of Bristol, November 3, 1774.)
As for your fears about his Church telling him what to do, this is a point I'm puzzled about. Why would you find it preferable to vote for a man who publicly betrays a faith he has sworn to deeply believe, rather than one who won't betray it? It seems the former is self-evidently dishonest.
This is not some arbitrary papal pronouncement. It's a fundamental teaching of the Church. The letter above makes clear that the statements of the pope himself regarding issues such as capital punishment and war do not and cannot bind Catholics this way.