I really need some advice?

Why are you listening to him as if he brought her? If he wants to keep the cat he should give you the 60 dollars back. If not, return the cat

The last two problems are easily remedied; don't touch her tail and don't pick her up. Many cats HATE this. Just stop.

She's feeling your tension. You want a happy cat? PLAY WITH HER. Like, a lot. Many cats that act out are bored and don't have outlets. Get wand toys and become more interactive with your pet.

Also, learn to pet her how she likes. When she's being sweet, stick out two fingers to her face, let her sniff your fingers and she will most likely lean into your fingers with a cheek or guide you under her chin or her ears. That's what she wants. Pet her for a few minutes and stop. Cats can get very over-stimulated very quickly and easily; they are not dogs that like constant touching and petting. They enjoy affection on their terms and will come to you.

I think your real problem is that your fiance is not somebody you should marry and have children with.

He won't let you TRIM her nails??? WHY?

Tell him the nails get trimmed every week and spray bottle training will be used or the cat can't stay. You're not a woman from 100 years ago--stand up for yourself!

Next: the cat needs lots of play time, consistently with wand toys. Get the extra energy out and it will calm her and help her bond with you.

A lot of cats don't like their tails touched at all, so don't do it. Some cats come to you, not you to them. Don't pick her up if she doesn't like it. Spray her with the water and say no in a deep firm voice when she scratches you. Treats are never to be given after misbehavior. Find a moment of kindness later where she is behaving well, and have treat in your pocket ready to go. Cats are trainable and will bond easily with those who feed them over time. It takes patience and you will have the cat that you want to exchange the cat for without feeling terrible about yourself.

Don't misuse the spray training or use a newspaper on the cat. No spraying in the face or eyes either.

Still, that fiance is not the person you want to EVER have kids with if he can't grow up and compromise on how to "raise" even a cat.

Your cat is reacting to touching she doesn't want. Touch that in the past caused injury or pain to her. it's not her fault. Living with an animal is a compromise, they're not all sweet docile things. You love them for who they are.

I have one who actively leans away from any hand reaching out to touch him but he loves being picked up. So I don't pet him, I lift him up and we walk around the room a bit before I play with him. That's ok.

Take the cat, throw it in your fiancé's face, and enjoy the entertainment.

It sounds like she is bored.
How often do you play with her?
Just like a dog needs a walk daily, a cat needs active time every day. Get a feather on a string toy and play with her. This uses all of a cat's natural skills. Play with her until she is panting and laying down, then let her rest. After a few minutes, start playing again. Get her tired. Get her used to a play time. She will be happier when there is more structure about things like this.

Kick your fiance to the curb.

You have a fiancé right? Do you know what the definition of love and loyalty is?
When you get an animal it depends on you for the rest of it's life. You are asking hi m to abandon that cat and have it killed. Is that the type of loyalty you want from others?
Get a feliway plugin which is a pheromone and may help her relax. Don't touch her tail and google cat's ears and cat's tails so you know what the cat is saying to you

U re not a good person