i dont see any difference in the site performance between http versus https.
regardless, if you are seeing a difference, that would be on the server side, and not on the code side, the code wont act any slower or faster when access via http versus https.
We cant help with server setup, you will need to work with the host for server set up issues.
regarding you comments about SSL, yes, with shared hosting it will use a subdomain URL for the secure site. If you are picky about that, then yes you need dedicated hosting, that is the way it works.
sorry to hear about your troubles with 1 and 1, you are the first person I have heard from that has had a bad experience.