I am so sorry your kitty is so sick. Unfortunately he is beyond home remedies and you cannot do anything to help him. He needs to see an emergency vet immdiately and he cannot wait until next week. I suspect that he is extremely dehydrated and malnourished and I worry that he will die if he doesn't get help today. He needs to be hospitalized, placed on iv fluids and antibiotics, pain medicines, and may need a feeding tube, blood or plasma transfusions. Some mushrooms cause the kidneys to shut down, and this is a very slow and painful way for a kitty to die. Your kitt is suffering and he needs help right away. If money is tight, you may be able to apply for care credit, depending on your situation.
Please let me know if I can be of further assistance. If this has been hlepful, please hit the green accept button. Good luck with your handsome man, let me know how he does.
I am so sorry about your kitty. It is frustrating that the majority of the damage incurred from mushroom ingestion is pretty much undetectable in initial stages. I am very sorry he did not make it.
Insurance is great, but keep in mind that you still need to pay the vet bill up front. You get reimbursed after you submit the invoice, and you will probably not get as much money back as you think (speaking from experience). Insurance is till a great idea, so go for it when you can. I will keep you in my thoughts.....