Live in relationships enjoy certain protections that marriage does including the child potentially inheriting property, the application of domestic violence act, etc.
However, two people in a live - in don't enjoy the same sanctity in marriage (as of now, but I see it evolving generally, internationally, it's called Common Law Marriage) like spousal privilege or being each other's legal heirs, agents, nominees, etc
As for 498A, that's a tricky one, any criminal proceeding depends highly on the facts and you need to tackle them accordingly.
Try and make sure your conversations over text include the girl explicitly consenting in multiple situations. If your relationship includes physical intimacy, try and discuss the various acts you're comfortable with over text. If she consents to oral sex but you go for anal (which she doesn't consent to) that's rape too. Keep communication open and flowing.
Look, as much as this scares men, the real possibility and statistics of women falsely accusing men is very very low. I'd really recommend to be with a woman who understands what casual relationships are, employ the same tactics a woman would to ascertain if the guy's a psycho.
A woman coming from a conservative family or environment may still enjoy the benefit of doubt, but the court has repeatedly held modern day dating and breakups can't be held to the same standard as rape or sexual offences.