Earthborn, each of your examples might be
primarily answered by the "faith magisterium" (or whatever), by most people, today. But, there is no reason why science can not grant us insight into them. At least in principal, (and I suspect in practice, as time marches on).
"At which point does a foetus become a person worthy of protection?"
Science shows us that there is not a single "point" to worry about, but rather a gradual process of development, that deserves a gradual issuance of protection. Where the "lines" of such protections are drawn can change over time, depending on human interest and need, and of course: further scientific research.
"Is it moral for a hungry person to steal a loaf of bread?"
Game theory can give us insight into the risks vs. rewards of stealing something, for both the individual and the society at large. We can mold and shape our moral codes and laws based on what works out most efficiently, mathematically. Much of biological evolution is based on this kind of stuff.
Social sciences could also give us some insight, perhaps in a more general, less mathematically specific way.
"What is the purpose of life?"
Life emerged as a consequence of natural forces acting on naturally occurring self-replicating systems. Our "purpose", if there is one, is ultimately determined by our evolutionary heritage. Which basically amounts to "reproduction!!!!", for the most part.
How your genes helped you develop their own, specific survival strategies for doing so, is largely based on the particulars of both your genetic heritage and the particulars of your environment. And, sometimes this results in life forms that do not reproduce. But, even then we can trace the reasons why back to all those particulars.
Any other "purpose" one can say they have stems from all that stuff.
The candidate with the best science policies.
"Should I eat another piece of chocolate cake?"
Like the "stealing bread" example, science can help us measure the risks and rewards for eating yet another piece of chocolate cake. The social implications might not be quite as relevant as the other example; but one can measure the caloric intake and weigh it against the happiness they would feel about eating it, etc.
You might argue that few people are going to pull out calculators to actually go through with all the science stuff. But, my point is that science can still answer these questions,
in principal. They are not "faith only".
ETA: JoeTheJuggler's examples were better, but less relevant to anything that really matters.