Hi Riana welcome
I try to answer some of your questions as I noticed as well not much written information about the cattery is present.
To give you an idea 100L = 250K$
k$ can be either obtained via a gift card, if you click the card the value will be credited to your K$ balance, you can pay your free obtainable Cattery Dock with lindens and your account balance will have K$ currency.
You can collect K$ as well via bringing cats or boxes, which you don't need, to menagerie via the dialoge menu this will credit you each time with 50K$ (bringing cats and boxes to menagerie removes them permanently).
The K$ can be spend in the KittyCatS store on everything but furniture as well as in your online cattery and in the future there will come a special shop with items which can only be obtained with menagerie K$ and for this reason K$ obtained via Lindens or collected via bringing cats or boxes to menagerie are displayed seperately within your account on this website here you can see all your K$ transactions as well:
http://kittycats.biz/transactions.php
First your obtained k$ will be used if you shop with them and then the menagerie K$.
I also noticed the screen within the online cattery, when you attempt to obtain something does not close unless you actually buy something, I work around this by refreshing my browser I heard though this is to be fixed.
To answer the question about how much food your cat needs this is one bowl of food per month per cat.
Though when you obtain a starter cat or special edition cat they have food included as well and these are less strong and will last a week these bowls are blue while the regular food bowls are not.
Bowls of food are obtainable in the online cattery as well as in the KittyCatS Main Store for your in world cats.
Here you can buy 1 bowl of food 10 or 20 which feeds 1,10 or 20 cats one month.
The online cattery and the dock have no extra cost and is therefore just an other option in how people can breed.
Ofcourse feeding cats goes in the Online Cattery the same as in world.
I hope I was able to answer some of your question and welcome again in our community