Ok, not sure how you got that tyk.conf, you can compress that http_options down to just this:
"http_server_options": {
"enable_websockets": true
},
I think that some of the other options there might be interfering, if in doubt, use this as your base template:
https://github.com/TykTechnologies/tyk/blob/master/install/data/tyk.with_dash.conf