Hi LilisMom, I'm sorry things are sounding so hard for you right now, and I can guess that everything is feeling like too just much. I may not be much help but, my best shot........
Firstly, my condolences for the loss of your mom. Whatever your relationship it must have raised a lot of feelings for you
And.......it does sound like you have a lot to deal with but maybe separating them and trying to deal with one thing at once might help a little???
Then even if one thing can be dealt with it might take the "pressure" off a little???
For the antiques/collectibles..........maybe your sister could lend you some money to bubble wrap/send a couple of items if you just start with selling a couple then the money you make could fund you paying back your sister and sending more items. I would check out some of the free online appraisal/valuation sites first though, just to make sure that any offers are "reasonable". And unless you want it too, everything doesn't all have to go at once, if you can just for now work on clearing the living room at least???
And cookbooks........sorry I have no idea.......do you think some of them may be valuable??? If not though some charities might pick some of them up if you would want to give some to charity??? Or you know, maybe if there are jumble/yard sales in your area you could phone up and see if they'll take some to sell for a cut of the profits??? Sorry I'm a bit lost on that one..
And the cats..........maybe if you stop feeding them, they'll start going somewhere else to find food??? Otherwise maybe some pet rescue center could collect them/some for re-homing??? You could always keep one or two if you wanted to, sometimes pets can be a "comfort".
And back to you, it sounds like the counselling wasn't at all helpful, but if you want people who have lived through/are living through some of the things you're going through, then here is definitely a good place to be, especially if you'd be unable to find/attend any support groups in your area right now.
And there are quite a few forums that might be able to help e.g. Post Traumatic Stress; Anxiety, Panic and Phobias, Grief and Loss although you may well find others helpful too, (as well as this forum!!).
Anyway, welcome to PC, and I hope you find the support you need, there are a lot of great people on here who are really understanding and supportive so please don't hesitate in sharing what's going on for you, with us. We're here for for you.

Alison