((((Concerned)))) you have us and you have PC. Don't give up. You are doing the best you can under the circumstances (which are for sure very challenging).
You are not alone and you can count on us for support. We have all been through one thing or another (or a bunch of things)...challenges caused by pain, heartbreak, uncertainty. We all want to do the right thing. That is why we are here, as well.
Try to take it one day at a time. You mentioned pregnancy and hormones & and your daughter has a history with this person. Good or bad. The bottom line is that ultimately she will do what she wants to do. Which I do hope is to stay away from him. But she is an adult (kind of...I have a hard time thinking of a19 year old as an "adult". The world is a lot more complicated and much more challenging than it used to be. And she is still your child. She will be your child no matter how old she is

)
If you keep anything in mind, front and center, remember this is your home. Your safe place. It is important that you take care of yourself, though, and stay safe. And try really hard to adhere to your boundaries and what you are comfortable with.
(If you need to, make stickies with affirmations for yourself and post them where you can see them at any given time).
Dont let this man control and manipulate your life, as well, while he is playing mind games with your daughter. Be there for her and the baby. But also be sure to communicate your feelings and stick to your comfort zone.
I have a feeling he is going to try to weasel his way into all of your lives, and your home. Esp because he is without a job and home. He WILL try.
Ultimately, the buck stops with you. And you are coming from a good place: love and care. But if you cave to his manipulations, things will get way worse than you being fearful of him as a person outside of your home and life.
If your daughter decides to let him back into her life, she will have to do it outside of the safety and comfort of your home.
(I did have an experience with someone similar to him,.as.I mentioned before. Trust me when I say no good can come of him entering your lives. He is dangerous and toxic).
We are here. We support you. You are safe for now. As long as YOU set the limits.