Firstly those paintings are beautiful!! I love cats aswell ( second to horses tho, lol )
The thing about using your art for living off is...........its incredibly hard. There is sooooooooooooo much competition out there its rediculous. But that's not to say you can't. The biggest thing you can do to make sales constant enough to live off is to make a name for yourself in some way. You will really need to get your art out there.
Since you love cats maby get hold of some cat shows and advertise your work there. This will get you into the right audience , also pet shows will be good too.
As for making a handsom amount, lol. Well it depends on how much you charge, how big the work is and how frequently you can produce it. Because as an artist there is a huge gap of no income from when you beggin the work to when you finnish if you arnt working any were else. And if one work takes weeks to months....well will you have enough money saved somewere to support you during that gap?
I have an Uncle that lives off his art. He works for months then has an exhibition, then a break then gets back into work for another few months ...and so on. He sells much of his huge paintings for over $2000 NZ dollars sometimes, and often has about ..maby 5-6 paintings in one exhibition..sometimes more. But it took him along time before he got to that stage.
Maby get a part time job to help with every day expencises while you first start out on your art career.
Good luck. Your work is amazing.