I guess it depends what your understanding and expectations of love are. This will be different for everyone.
Personally, I think it's rare to meet someone you fancy, who's funny, smart, attentive, patient, adventurous, wants the same things as you at the same time as you etc. Then grow older with them, have children with them, and keep that level of attraction, love and unity. In films maybe but not in real life. I think over time love normally changes to friendship, albeit with occasional sex and cuddles. I think trust, reliability, laughter, honesty, openness and shared history are so much more important in a life partner. But that's me of course.
Have you had therapy OP? Before throwing away a fairly successful marriage (albeit it doesn't feel like one to you), I would have some time to explore your history. What you value. Where you want your life to lead.
You owe it to your daughter, before turning her world upside down, to be sure of your decision either way. And to tackle your depression the best you can. Then, if you are still sure you want things to end, you'll be in a stronger position to do it.
If you end things now, with doubt still looming, you may regret it. And with children involved, it's not a great mistake to make.
Perhaps be honest with him. Tell him that you're having doubts about the relationship but you're not sure if it's the relationship or depression speaking and would like some therapy before buying a place. Sell your flat, rent and see how you get in over the course of 6 months.