Starting, you had a really really tough start into adulthood. It's totally understandable that you would appreciate and invest deeply in whatever adult was there to love you and support you at the time through that.
It's confusing when someone takes that sort of role at that sort of pivotal moment because one of the things we feel is that our parents should love us unconditionally. This can be transferred onto a partner quite easily, particularly in the cases when parents have gone. And the fear of abandonment becomes utterly heightened and devastating. No partner loves unconditionally as a parent does, nor should they. you should not love him unconditionally even though he cheated on you and is lying about it. he does not love you unconditionally and has decided to play away. This is heartbreaking and reminiscent of a lot for you.
Most people being left can say 'oh well at least I have my friends, or my family or my job, or all of those'. but you have been particularly badly treated because you have lost a lot quite young. That does not mean he is all you have. In fact I think maybe he's been keeping you from having a lot of that stuff.
I think you already know that coming to do the roof stuff is definitely a subtle way to keep control and ease guilt. He would get to look in on you most days, which seems caring but isn't because you can't look in on him can you? Hell, he wouldn't even tell you who she was? You are the child in this relationship and when you come here and talk to us having recently seen him you even have a voice more like a child. But the wonderful thing is that even after an hour, that fades. you literally grow the further from him company you are.
Let me ask you this, if you said to him you are going to get your head together and stay with someone, without telling him who, but of course you would still appreciate he finish what he started in the loft, do you think he still would? come in ever other day and work on it, in an empty house?
I would like to think he would, because that's exactly what he should do morally and would be the best thing for you too. but if not, think very carefully about why not. Of course he likes to feel you need him, you've already said how he likes to feel 'like a man'. Well now he has two women saying he loves them and two beds and a handyman job where he can come round and make sure you're not having anyone 'sleep on the sofa' and then he can go back to god knows where and live his other life.
He would have to BEG, BEG for you even to consider getting back with him after what he's done to you. And yet it's all about his uncertainties, his insecurity, his judging of you. What does he think is going to happen in the next few weeks? That you will become a different person? That he will? no, he just thinks if I can keep both options open that would be great until something resolves it.
Soon, OP, soon, this has to stop. Give it a week to get your head right and then you are going to get properly angry and properly in charge of your life. You have a whole new life on the horizon, whatever way, not with a parental substitute who cheats on you and not with no friends and no job. All of that has to change, so you may as well do it without him. You have had a lucky escape, bright and childless and a home owner. Getting back with this man would probably be a prison for you. It has given you what you needed, security through a difficult time and someone who represented love and support. But maybe it's time to let go.
Someone will love you again. I promise. I have seen it happen every time. You have already had a really tough break in life and you got through it to become a decent, kind, clever person who has assets and opportunity. You are actually strong.
You are not losing your parents again. I promise, OP.
You are going to be okay.