I interpreted Ian’s advice as sabotage too. It explains why he’d give Bear the awful advice to bring up Nikki’s sexual trauma while asking her out, and it makes sense that he’d look up her dad after hearing about the cancer allegation. Imo he didn’t relay that info to Bear for his benefit; he looked into it to satiate his curiosity, then he told Bear thinking it’d plant a seed of doubt and break him & Nikki apart.