My LD BF won't even acknowledge it inappropriate

My LD BF moved out of share house with female housemate
We have been together nearly two years. In January, he took a job 2000ks away and rented a room in a share house promising to fly home whenever he could and this was only until he could find a better job.
I have seen him five times since then - we chat or text every day & the love and connection were still strong... until this point. I cannot reconcile his recent decisions with a commitment to our future all of a sudden.
After he'd been away 3 months, this girl started popping up tagged on his FB time line - a young, stunning girl at that. I asked who she was & he told me she was one of the housemates.
He also had two male housemates, however the idea of him sharing a home with another girl who got to see him every day & hang out while I went months without seeing him really hurt and did not sit well.
He told me she was nothing to worry about and reassured me I was his one and only who he wanted to grow old with. I clarified that it wasn't the fear of them hooking up that was driving my problem with it, rather that it offended and trespassed on the place in his life I could not share and was dreaming about the day where I could see his goofy smile every morning & felt so unfair she had that luxury instead.
Months passed, and he came back to visit for a week. Day before he flew back he took a call about furniture being delivered to a new house instructing that his housemate Jess would sign for it.
I asked him about it & turns out he and Jess had moved out of the share house and we're setting up a new home together.
He told me he didn't make a point of talking to me properly about it because he knew I'd be upset.
So he paid all the bond, had bought furniture, and was signing lease day he got back.
I was so upset. I told him I was NOT okay with it, he needed to get his bond back before signing any lease and find somewhere else or tell her she had to.
He refused. Said she wasn't a problem. Made excuses. Paid $1400 for airfares so I could meet her that weekend and see for myself. I was ready to break up with him at this point.
I tried to be okay with it but I just couldn't. They both had told me very inconsistent information and the requirement for such shiftiness alarmed me.
I had to lay it out straight - one of them moves out and cuts contact or I couldn't be with him anymore.
More excuses and vague references to plans of finding another option at some stage.
How is anyone expected to be okay with this?
He swears there is nothing going on and he's not attracted to her, that they're just friends & if they didn't get along wouldn't be housemates. He further drove the point that they barely see each other, she respects his privacy and spends most her time in her room. "Pretty much share a kitchen and bathroom, that's it."
But I spent a good deal of time talking to this girl & taking her measure, she's as up to date on his current affairs as I am - technically she'd get a quicker update than me, getting to live with him.
My man has always had a strength of integrity and principles that I've never seen him deviate from at all. I have admired and cherished these things, it allowed me to put all my trust and faith in him.
This situation has blown me away, being deceptive or outright lying goes against everything he stands for. Everything I've known him to be.
Yet the fact he went ahead with this move in the first place knowing I'd have a problem with it, without even trying to make me okay with it first, completely contradicts the pledge of undying and devoted love he still makes to me this very day.
In his previous share house back home one of his housemates was a former romantic interest of his, I didn't have a problem with it.
It's all the evasive behaviour towards me regarding her, and that this housing arrangement was the most expensive and inconvenient option of so many.. There are so many rooms available to rent in established houses there at the moment as it's a mining town where shutting one down rendered 1200 workers redundant and shipping out for work elsewhere.
The Monday he was home he was dreading the possible redundancy call himself - he was lucky to be one of the few to keep his job for now.
Thing is, he had fronted thousands in bond money and setting up the house the week before he came home - when he wasn't sure he'd have a job to come back to. She was already in.
Why set her up so comfortably? And why can't she find her own bond and rent money.. and has nothing to her name not even a car.
She is taking advantage of his kind nature, and increasing the pull with batting her lashes and playing best friends. I found her cunning, but not overly intelligent and very transparent. Not genuine.
He thinks she's beyond reproach for some reason and he's fought harder to keep her in his life than what he has to keep me and repair our relationship from this.
. Even if he really has no attraction for her, the whole scenario is very susceptible for growing something much bigger as time goes on.
I've sacrificed my self respect and dignity laying it all on the line, and telling him that I needed him to make his choice and set me straight on it right now because this has been a month of crazy making heart break for me.
I can't take the anxiety anymore, and the reluctance to take a decisive step that deviates or compromises at all hurts more with each passing day.
I ended up telling him it was decision time - her, which meant breaking up with me and being honest or stay with me and sever contact. He refuses to even move out, or make her leave instead [frown]
I can't understand why this is such a hard decision for him while he adamantly reiterates his heart and future are mine alone.
What would you suggest here, is there anything I can do aside from suck it up and fall to pieces or cut him from my life completely? I can't see other options despite desperately searching for one.