Reading the script helped me map things out a bit better. I think part of the confusion is that Tini did mess up a little bit with Blade's timeline. When he was wearing the old costume she had him wearing, she hadn't met Black Panther or Iron Man yet.
The kidnapping thing makes sense. Seems like the victim needs to know about the Vridai for them to take their form, which is why they have to kidnap people.
Monica met Blade in New Orleans when they teamed up with Dr. Voodoo, Black Panther, and Luke Cage, then they were on the New Avengers together. Blade's never been written with the others, except Hellstrom.