I[22F] remained best friends with my ex[18M]. Is it possible for a compulsive liar to change? 1.5 years.

First off, apologies as this is my first post on reddit and I have not slept yet. Also, apologies for the length, but I would be so grateful to get some insight on this.

A little background:

We met a year and a half ago after he saw me in a mutual server on a text/voice chat app and messaged me out of the blue asking if I'd ever want to hang/talk with him sometime. We started talking, became very close talking everyday, and ended up becoming exclusive 3 months later. He lives in Canada and I live in U.K, so this was going to be long distance for at least a while. That was the plan anyways. We had plans to meet 3-4 months after, in the summer of that year. I was going to fly over and stay there for a week to be with him.

Now, I'm going to start with the biggest lie. When we first met, he told me he was 18, close to turning 19. Fast forward to the summer, not long before we were supposed to meet, where we were talking on skype. His mom was in the same room working, and I basically found out from her, not realising that he was in the call with me, that he was actually 17. This means that he was 16 when we first met. I was beyond devastated and felt disgusted with myself. I was angry with myself for being so stupid and naive, him for lying, and also at his parents who supposedly knew the whole time that he was lying to me and thought this was okay for him to do. I asked him when he was even going to tell me, and he said that he wasn't going to tell me until I had gone over there to meet him. I would've wasted so much money just to fly over there, get hurt, and then go straight home. I feel as though it was so selfish, but this is what I got for trusting a stranger online. I'd like to add that before even becoming exclusive or thinking about going over to see him, I tried making sure I wasn't being catfished or anything like that. I saw him on webcam plenty of times, I talked to his friends, things like that. Everything seemed legit to me and he didn't even look/sound 16. Anyways, after this I broke things off with him, and we remained friends.

Before that, he would lie about silly and unneeded things such as who he was hanging out with, him talking to other girls, what he'd been doing. Things like that. I never gave him any indication as to having problems with him hanging/talking to other girls, let alone other people in general. In fact, I always encouraged that he should spend more time with his friends and that some time apart would do us good. I realise now of course that I was talking to a 16/17 year old at the time, so in terms of maturity, I probably shouldn't expect much. I asked him why he lies over silly things, and he explained that ever since he was young he has lied many times as a means of getting out of trouble with his parents, and now it's just become a bad habit. I can believe this to be true as his parents are insanely restrictive and controlling over him. He tells me that he lies to me because he doesn't want to upset me or cause arguments, even though the arguments only started after I found out he'd been lying about such things.

Fast forward to today. Although we remained as friends after, the whole time he has made it clear that he still loves me and eventually hopes to get back together in time. Not that this means much anyways, but as a way of showing me he was serious and "only wanted me", he changed his facebook status to "in a relationship" and kept it that way only for me to recently find out that he had posted it with it set to "hidden" and not "public". I don't use facebook much and I had just trusted his word at the time. And yes, I know I'm an idiot. This is just another example of his kind of lies. I'll be completely honest and say that despite all the lies, I never lost those feelings I had for him. However, I've accepted that we can never be more than friends due to his lies. Ever since then the lies have continued, and despite making it very clear how much they hurt me, he carries on, each time telling me it will never happen again and that he's so sorry. He's like a broken record at this point, and then there's me, believing that he will change and forgiving him. Mentally I am drained. Second guessing everything he says and all these doubts running through my mind constantly has taken its toll, and now I'm at a point where I'm not sure I can even remain friends and if he will ever change. What hurts is that if it wasn't for the lies, he would've been my dream guy. He treats me like a princess, goes out of his way to make me happy, even as friends. We talk everyday and in general he makes me so happy. I find it hard to imagine my life without him in it. After he lies he will go all out to get me to forgive him, he will cry, and to me he genuinely seems apologetic. So, I give in.

After finding out yet another one of his lies today I'm sitting here wondering if anyone has had any similar experiences with someone like this and if there is anything I can do to help him stop. He genuinely seems like he wants to stop, but at this point I'm not even sure. It's been a year and a half now, and there hasn't been any improvement. Is it even worth keeping him as a friend at this point? Thank you so much in advance.

TL;DR remained best friends with my ex who is a compulsive liar for the past year. We broke up because of his lies. He has supposedly been trying to stop this habit of lying for the past year and a half but there's been no improvement. Can I even help him or do I cut him off for good?