I think the chaos of the moment and the delay between uploads is taking away from what we are supposed to understand. Sure there might be a metaphor here, but also remember they mentioned that the more these two spend time together the more people will forget Yoshiki? I think his dad was 1) trying to remember him/coming to terms with his memory gaps 2) making a jump decision in a very short amount of time to side with what his “whoever this is that my heart says I care for” thing wanted against the horde dragging him back. Hence Yoshiki pointedly saying “dad” and leaving last words for him. Because you’re right, most parents wouldn’t put their kid in the maw of an unknown monster but he didn’t know WHO he was just that he was SOMEONE to him.

Ah bzsufdjcfbincgakd there is no sense in Yoshiki's dad letting him go to a bizarre mass of who knows what like he understands everything... But guess this was a analogy for 'helping your son get out of the closet' :V