An ex-gangland gunsmith who renounced violence after converting to Islam faces an impossible dilemma ? to save her estranged family she must help extremists assassinate the US President

You’ve got some great bones to your logline – punchy description – it makes me want to see the movie! A couple of suggestions:
1) the “who” throws me everytime I read it, maybe switch around the sentence to read “After renouncing violence in her conversion to Islam, an ex-gangland gunsmith…”
2: I love the word “dilemma” but what you’ve stated isn’t a dilemma, it sounds like you’ve already chosen for her…. dilemmas are choosing between this or that. She can chose her new faith and let her family die or choose to save her family by assassinating the President.
Great job though, there is a lot of action packed into a short sentence! Not an easy task.