If you two are in love and your family is abusive would living with him be an option?
Sorry to jump off your comment alone but any parent who would be okay with their 18 year old dating a 45 year old would have to be off their rocker, I don't see how parents being horrified by that are considered abusive. And so far the only thing they've been accused of is a potential thought crime of wanting to attack the man for taking advantage of their kid. I doubt what the OP says regarding them coming after the OP themselves with violence. Toward the guy? More likely, also more understandable. But toward OP? I doubt it. They would probably just be bewildered and frustrated beyond belief. There is no stopping being young and dumb, and this 45 year old man knows this.
I know people are trying to be supportive here but Jesus Christ, sometimes people support the worst decisions and viewpoints on here just for the sake of support and surprisingly scoff at other viewpoints that are much more worthy of said support. It's very bizarre.
Lawful consent often means nothing in the grand scheme of things, so although OP may consider themselves an adult, to me they are still a child, and I am sure that is even more the case for their parents. Most, if not all, relationships are based on some unsavory things like superficiality. But age gaps like this take it to another level. "Love" has nothing to do with it, it's a flimsy farce to justify things that just should not sit well. Men (or women) who go after people who are so much younger are chasing youth and naïveté to the extreme, the power imbalance, the experience and knowledge imbalance which should not be combined with a sexual/romantic relationship. The fact that their very life expectancies are over a quarter of a century away from one another..
Not to mention OP was friends with him before they turned 18...come on OP, he was waiting for you to turn the legal age, he was never your friend, only someone preying on you and waiting when the time was right. Honestly after what some other comments have pointed out (you've been with him for 1.5 years?), I doubt he even waited until 18. Be honest with yourself. Even if he was just suddenly struck with Cupid's arrow, something has to be seriously out of whack with someone his age to engage you and enter a relationship like this. Even people who want to test the waters would at least have enough sense not to, if even for the simple reason that yes..it is highly frowned upon.
What is his occupation? How did you meet him? At what age? Where are his own friends and family in all of this?
OP you say you've been groomed 4 times so you would know...well why didn't you know after the first time? Obviously it was not your fault but the question still stands. Why is the 4th time the charm? Because you are older? Well you're still very young! It it known that many groomers almost sense those who have been previously groomed, they don't avoid them for fear that they know the techniques, they seek them out as easy pickings!! And this fact causes the victims a lot of grief because they wonder "why them" and "what did they see in me that was vulnerable"..it is all very unpleasant but it happens that way all too often.
People also don't all groom in the same way. You say only love could be his reasoning for staying with you after all you "put him through" but I think you underestimate the power of Lust and even love itself by many definitions, can be extremely problematic. It's not a good excuse to be in an age gap relationship, especially of this magnitude, with you barely encroaching upon young adulthood. You think he is an idiot for staying with you, you're right! He is! Why do you want to be with an idiot?! I guess it's better to be an idiot than a pedophile, but my god I think we may be dealing with both here. You say you're not the type of person someone would be with just for the sex? Okay what type of person would that be exactly? Why are you special? You think his love is unconditional, but you don't realize that one of the conditions may be the age gap itself. He wants it.
At this stage, you can and will do what you want no matter what anyone says but I think there is also a lot of information still missing from this story. As far as the suggestions to call the police? After what I've read on this thread, I am pretty sure that would only get you and your 45 year old bf into hot water, not your parents. Unless you outright lied to them or this man you are with has connections.
Sorry to be blunt but this whole thing is just a big giant Yikes from me.