I found SLITHIS terrifying at age 11. I was old enough to know better, too. When I finally got the chance to see it again of VHS a few years later, the magic was gone. It's horrible.

The survival kit is as you describe it. The card from the movie theatre was yellow, IIRC, folded in half with nice Slithis art on the front derived from the poster. I believe you were supposed to cut off part to send for the photo, and keep the remaining bit under your pillow to protect you from Slithis. Never saw a vomit bag.

The film will be playing at the New Beverly Cinema in Los Angeles in April.