Does this work well on clothes/fabrics that a cat may have been around? Or just for the cat's physical body?

This is Steve from Allerpet. Allerpet Cat Dander Remover is the catalyst and allows the dander to be transferred off of the animal's body and onto the cloth or microfiber towel you've wet with the product. Then just launder the cloth and the allergens will be removed. It is not designed for use on clothing or fabrics.

Is regular bathing required when also using this product regularly?

I didn't bathe my cat in addition to this, I only used this one a week and we had no issues with the allergies so I'd say no.

How much do you need to clean one cat once? How long would one bottle last I guess is another way of asking the same question.

Our cat is roughly 30 lbs which is huge but we damp a cloth and rub places he can't lick like his back once a week. A bottle last months for us.

what are the ingredients? (preferably a picture of back of the bottle)?

I don't know the ingredients, but I use it at my professional dog an cat grooming salon. It does what it claims, my customer that allergic to there animals ,we use on there pets it neutralize the pet dandruff. Moore pet allergy when you use aller pet