Urgent Help Needed for Marley's Treatment

Hi, my name is Christine and I’m looking for help for Marley… my best friend. I never had a cat before but my daughter brought him as a tiny little kitten, my dog Dakota helped raise him. He warmed my heart and I fell in love. Daughter grew up, Dakota passed away of old age. So Marley is my “person”. He greets me everyday when I come home, almost like a dog. It’s the 2 of us living solo. Recently He had a bad reaction to flea medication Cheristin. He has had IVs and antibiotics and sent home to recover. He perked up but is now declining. Which quite honestly breaks my heart. I am the biggest lover of all animals‍⬛ I always try to help others. He requires more intensive treatment and I have already paid as much as I can. He’s my best friend. I hate asking for help but I am humbly asking for any kind of help. Thank you and blessings to all