Ginger, I am so sorry you're hurting. And I'm very sorry for your D, too. I hope you can do something fun together to take your minds off this for a bit.
I wonder if maybe FF got scared with the pace this was progressing at. It's not an unusual fate for a new R that is this intense.
I don't think you have to wait a year to introduce your D to someone you date (or wait until she's 18 to date!). But you don't have to introduce them as a partner very quickly and allow emotional bonds to form between them, either. It's not an either-or situation.
Next time you meet someone you like, I think getting a sitter and limiting the time you date would be ideal. When you know you are an all-in person, limiting time and GALing like crazy can be your savior (I'm an 'all-in' as well, but getting it more under control).
I'd wait 3 months or so to introduce a person you date. Having a strategy can make you feel more in control, too.
M 16 yrs, WH62, P54 3 adult blended kids EA 11/13, BD1 6/14 PA fall 14, BD2 2/15 Piecing 2015, BD3 12/15 Separated 4/16 WH moved OW in 5/16 Divorced 6/15/17