As per title, how do I delete this account?
According to this topic on the discourse meta site you should be able to delete your own account if you have one post or less.
provided it has 1 post or less. See the bottom of your user preferences
Otherwise you need to contact and administrator or moderator. I think the rational is that deleting accounts that have posts could leave existing discussions in odd states.
Sorry to hear you want to leave. If you have the time I would love to discuss the motivations and see if there is anything I can do to help. However, I can appreciate that everyone has their own choices to make. I will wait for your confirmation, either here or privately before taking action.