Cat Behavior Issues ... HELP

This past summer, I rescued a feral kitten. I found her in my subdivision, someone dropped off a whole litter but she was the only kitty who didn't run when the neighbor's dog chased away the momma & other kittens. I was able to tame her in just a few weeks and adopt her out. Here is a photo of her (Luna) riding in the car & Yes she has 8 toes on each front foot: 


Anyways, in the last week of December, I saw a cat run past our back deck. I went outside to look and found out that a cat was living under our deck in below freezing temperatures (I live in Michigan). Two days later I was able to trap him, take him to the vet, and bring him inside from the cold. Turns out he is Luna's brother. He's 6-7 months old. I've had him (Nimbus) for almost a month now and he is making good progress. He will let me play with him (he loves chasing the feathers on the stick, and adores tennis balls), and occasionally he will let me pet him. I still have to use a thick glove to pet him because he will randomly bite, scratch, and hiss at me. 

Photo of Nimbus in the dog crate before he was let free into my room:


I have him in my bedroom now, I have a little cave set up for him, because he likes to hide, as well as a little cat tower in front of the window that he likes to sit on at night when the lights go out. My problem is that every time I come in my room he will hiss and charge at me until I sit down and give him food on my lap, then he is a sweetie, But then randomly gets scared hisses & swipes at me and then runs back to his cave. I've tried Nature's Miracle Calming Spray, but I'm not sure if it's doing anything. I really want to help him overcome his fear of humans, I need to adopt him out ASAP as I am allergic to cats, so I need him to be a good boy so a family will give him a chance. 

I was thinking about trying a calming collar, but I would have to get it on him. The Felaway Diffusers seem really expensive, I'm just a college student trying to give this cat a chance at a good life & can hardly afford food for myself let alone a cat. Let me know if there is something I can do or should be doing to make him less fearful and aggressive. 

Thanks! 

You can buy Feliway spray that is a little less expensive.  Spray the whole room and all surfaces.

You can also get Bach's Rescue Remedy and put it in his water or on his treats.  That has worked well with my feisty cats.

It may take a little more time to socialize this one.  He's older and he won't come around as fast as his sister.

You might start looking for a home now - with the understanding that they continue the socialization process.  Remember he may never be a lap cat.

Blessings on you for rescuing him - especially when you've got allergies!

Thanks for the reply Ondine! I just looked up the Bach's Rescue Remedy, and it looks promising, I'm really hoping something will work so he can be calm enough to feel comfy indoors and not scared or anxious. 

Good luck with your new kitty! I'm going through a process of my own with my little guy. So lost!