No, they've never dated.
I don't think Tangren could force YH to do anything, not now anyways, let alone forced him to delete his weibo post. He don't report to Tangren's ladyboss anymore. I know that fans pointed fingers at Tangren (which is understandable), but I don't think it's Tangren. I mean, YH have made numerous weibo post in the past that LSS is his goddess (yes, especially after leaving the company), and he have never had to delete his post before. I think it's more the his management company or the production company that produce the series he was promoting. I mean, if he was promoting a series and he have his OTP in that series, shouldn't he promote his OTP instead of another girl in RL? Just my thought. It could be Tangren that forced him, but I doubt it