However having divided everything up legally in terms of finances according to those Scottish laws, he can't quite bring it upon himself to take the step to actually divorce her. The only 'investment' he has in the relationship with OP is the potential financial benefit from investing in doing the work to the house and getting a free house out of it.
He's got NO intention of marrying you OP - ever. He never, ever will. You are just wasting your time and wasting your life.
Several posters have said that it looks very much like you need to understand, acknowledge and accept that the MH issues you thought you'd come through are still affecting you tremendously and they are making you EXTREMELY VULNERABLE to this utter con artist.
Keep seeing him for a few more months and see if he changes his mind? No. I bet you if you said to him well mate, that's it, it's over, he'd then start pretending that he would marry you - until he finally took control of your house that is - and then you wouldn't see him for dust or the offer of marriage would be revoked so quick you wouldn't even feel it.
However by then you'd have given away half of the inheritance your children should actually receive, to someone who never wanted or intended to marry you, and to his children.
Sadly though I don't think you've absorbed a single thing on this thread judging by your last post where you intend to continue a relationship for many months more in the vain hope that he will suddenly see the error of his ways and say my god OP let's get married!
So I think all I can do is wish you good luck because I can tell you, that's literally the only thing that will save you from this because you certainly refuse to understand that you are with a manipulative chancer who is after your money/property, but is most assuredly not after YOU. He has more interest (fake or otherwise) in his 'previous' wife than he ever will have in you - harsh but true. Believe it or don't, act on all the support you've had or don't - inevitably what you do or don't do is up to you but I hope for your and your children's sakes that you kick him to the kerb, but have a horrible feeling that's not what you're going to do.