You didn't move in because he didn't want you to.
OP you have two children to think of.
I would be very wary and I would not be planning to marry this man anytime soon.
He has delayed moving in with you.
It will be a massive change for him and for you and your children.
It often doesn't work out as the rough and tumble of a family takes getting used to, and isn't for everyone.
15 months after you were supposed to move in and still no conversation tells me you have absolutely no business planning a wedding.
Don't spend another penny on deposits.
You need to speak plainly with him.
You moving in with him and giving up your home puts you in a very vulnerable position.
You have two children to consider.
There is no place for a relationship where you have no idea what is going on.