[ryuurui]

The only word in kanji sounding ジャック is 惹句 (catch phrase).
Although, I suppose you could use kanji 惹 (attract), since you clearly want to woo her, and another one sounding つく, such as 筑 (an ancient musical instrument), and tell her a heavily stretched story that you seduce women by attracting them to yourself using your charming voice that sounds like an ancient instrument. To which she will go ええええええええええええっ！

As to Marika, as masaegu said, ask her, as there can be TONS of ways of writing this name in kanji. I give you one example: 真李花 (Pure Plum Blossom).