Hi, welcome to Pet Talk!
It sounds as if Sylvester is with you for quite a short time. So he may need some time until he fully trusts you and his new sister. Even young cats may need a time of several days before they talk to each other -with older cats it can take much more time.
Grisette who lived with me 25 years ago has spent weeks under the sofa until she became a family cat. I think it's a good sign that he looks forward to your coming home.
With his clumsiness this may be a different problem. I think you should see the vet for that. It is difficult to judge whether his deformation in the face comes from an injury. In this case he might even be blind on one eye. (In general blind cats are not necessarily clumsy but he's in a new environment, too).
Regarding Kona I am sure she's a little jealous that she is no longer the only cat in your heart. This may change with time (in most of the cases it does(Read the story of Jade Jaguar today) but in some cases, especially with older cats, the 2 of them will just organize their life so that they do not meet each other.
I hope things will get better soon because I am convinced Sylvester is happy to have a new and caring home.