Have you read my blog post linked above? Steps are in there.
You should make your fallback page https:, yes, but you don't want people to hit your fallback page at all. That's why you need the favicon redirect rule.
Again, I am waiting for a URL to test.
(I assume your domain is not "mycompany.com", though that is a private domain and shouldn't be used as if it's a placeholder.)
Jas, I don't think this applies to your situation because your company already purchased SSL Secure Landing pages from Marketo in the past, however, we just launched a new Secure Landing Pages product for which Marketo procures the SSL certificate. The end result is the same, so there is no functional benefit in switching to the new product, it's just a simplified implementation process. Everyone who is interested in this should contact their customer success manager.