Hi imaginedragon.
The blood in his vomit maybe trauma in his throat from continually heaving to be sick. Not sure about the other symton of blindness not heard of that before. If he will go to hospital he would benefit from a chest xray. To rule out infection. The Dr listening t9 his chest can hear crackling and any popping in the lungs which can indicate an infection. I am a semi retired nurse so have a little knowledge on chest infections, my only knowledge of cannabis is the psychological effects, anxiety and aggression. Hope that helps a little