Cancel now OP. Get it done so it’s not hanging over you all day.
Say you don’t feel comfortable with the situation and no longer want to meet up or have any further contact.
Don’t grovel or apologise, don’t over-explain, don’t get drawn into a discussion or any kind of back and forth with him. Just be clear and factual then block him everywhere.
I’m not sure murder would be my biggest worry in this situation, but there are many more ways in which we can be manipulated, exploited and hurt (up to and including physical and sexual assault), and our instincts are there to protect us from danger. Yours are on high alert for a reason.
Realistically he’ll likely head home once he realises he doesn’t have any way of contacting you. If he knows where you work, make sure your colleagues know you’re afraid of him so they can take appropriate measures if he turns up.
I know you’ve not been on it for a while, but as lots of people have said, a ‘cuddle site’ has ‘access to vulnerable people HERE’ lit up in flashing neon, and will be a magnet for every stripe of predator and weirdo. Make sure your profile is properly deleted.
Sorry you’re feeling so stressed and anxious, but it’ll be greatly magnified by the lack of sleep. Can you get yourself a few treats and plan a cosy evening and an early night? Could your friend come and keep you company?