Not sure what the question is that you want to address (mental health/relational or legal)
From a relational/mental health stand point- you should not do anything you do not want to do. If you've been dating her for a while, it is natural that she would have some sort of expectations. What is not natural is for you to give her or entitle her to your money. That is why there is prenuptial agreements.
You also have the issue with your daughter (but you may figure out if you're enabling her by allowing her to reside with you. She's an adult and would have to move on with her life and not overly depend on you. You've got your life to live and enjoy.
Your 24 yol son with the depression (hopefully he is getting help/treatment for that) You're not superman and there comes a time when you do what you want and what makes you happy. It is not healthy to be on the other extreme and just give and give.