Cat has developed dirty habits

This kitten we have here, a 6 month old male who I have not been able to afford to get neutered yet, is developing dirty habits. He started spraying on my chair in the livingroom a couple of weeks ago, and we knew he was only doing it when everyone is in bed so we have been putting him in the basement at night when we can't watch him. Now though he is peeing AND pooping on that same chair! I don't know what else to do with him, I tried confining him to the bathroom, but with people going in and out of there he kept getting out anyway. He claws up the door, the linoleum flooring, and my shower curtains if he is left in there also.
I tried spraying a repellant on the chair, it didn't work. There are 3 litterboxes, one upstairs and one on the main floor, and one in the basement, all are cleaned daily.
If anyone has any ideas, please let me know. I really don't want to have to find another home for him, but I can't have him peeing and pooping all over my house either.
I know neutering will most likely stop the spraying, but pooping on furniture is an entirely different story..... He is going to be 6 months on August 3rd, and has an appointment to be neutered August 11th, but there is no way I can do it sooner.

You really need to clean down that chair really good (getting all the scent out). You can try putting the litter box on it or under it for the time being hopefully he will use that instead. I've never had a cat that sprayed so I don't know how to handle that part. All I can suggest is trying a different repellent. Just like how not all humans like the smell of gas, some do. So perhaps your cat will need a stronger repellent. Feliway is supposed to work good, especially for marking.

Getting a cat neutered at a Vets office is quite expensive usually. Have you checked out the Spay and Neuter Clinic in your area? Most cities have one and they work in conjunction with the Humane Society and spay/neuter at a reduced price. The care they get is no different

I had my older cat spayed at the Spay and Neuter Clinic and the fee at that time was $50.00 compared to $110.00 at the Vet office in the area that I lived in at that time. I'm sure the price is a bit higher than that now, but probably still more reasonable than a vet's office, so you might be able to afford to have him neutered earlier.

The spraying isn't a dirty habit, this is what unneutred males do.

You have to get him neutered now, if you need help finding a low cost clinic in your area, there are people on this site who can help.

As for cleaning up, make sure you use an enezyme pet cleaner - it might smell fine to you, but to a cat's super-sensitive nose, it will still say 'pee here'.

ETA:
I think the pooing is a stress reaction to being locked up. Cats only have a limited range of behavior to communicate with, and sometimes what we do to make our lives easier makes things worse.

Clean your house throughly, buy a feliway plug in (the horomone should help stop the spraying and middening), spray the chair he's using with feliway spray, quit confining him and get him neutered. I practically garentee you'll have your happy kitten back.