I agree with you, and I question whether Maurice would be able to break the curse because his idea of loving his daughter is a bit twisted (and even Belle has clearly thought so as we saw in 204 when she temporarily cut him off). But remember who Belle is: She believes in the best in the people she cares about even when EVERYTHING is telling her not to. She is smart and she knows how magic and love work, bookwise anyway, but she also has intense affections for people, and I think it’s very hard for her to understand how someone could actually NOT love as intensely as she does.
She loves her father, therefore she believes in him and has difficulty seeing how it couldn’t be mutual or strong enough to save her from the sleeping curse.
It’s not a logical thing she’s doing exactly–it’s driven by her emotions of fear and love. She’s not trying to coerce Rumple; she’s trying to stop Hades from taking her child. And her faith in her father comes from her own emotions towards him, just as in the past her faith in Rumple has often done despite evidence that he was being less faithful to her (as in lying/clinging to his power, not cheating as in an affair).
Keeper of Belle's Gold magic, sand dollar, cloaks, purple FTL outfit, spell scroll, library key, copy of Romeo and Juliet, and cry-muffling pillow, Rumple's doll, overcoat, and strength, and The Timeline. My spreadsheet: https://drive.google.com/file/d/0B6r8CySCCWd9R0RUNm4xR3RhMEU/view?usp=sharing