Is it wrong to be paid to care for my mother-in-law to be and if not, what's reasonable and fair?

My mother-in-law to be moved in with us 4 months ago. She's 77 & suffers from Dementia & Parkinson's. I've spent approximately 11-15 hours away from her with my fiance since she moved in & always calling to check on here during those hours. Now, the only break I get is grocery shopping every 2 weeks & occasionally running to the convenience store (about 4 to 5 blocks away) for milk or bread between grocery tips. I've had to relocate all my clothing that was kept in the bedroom she uses. I've lost my recliner in our living room & cannot watch the tv in there because she does not like the shows, & do not get much opportunity to go downstairs to watch tv. I do shower downstairs as I have had to move all of my shower stuff & change my shower routine as there are constant interruptions. I take her to all doctor appointments, minus 2 or 3 since she got here. I take her to all therapy, neurololgy, psychiatry, etc appointments. I make sure she changes clothing & help her when necessary , bathes, washes her hair, help her make her bed, tuck her in every night because she waits for me to do that & so I'll turn off the lights, do her laundry, feed her breakfast, lunch, dinner & snacks. Make her coffee as she cannot pour it (this consists of several 1/2 cups every morning). Clean up after her. I'm constantly being stopped or interrupted. I can't walk in the room or go into another room without something being needed or talked to. She follows me around when her son is not here & is totally different with me than she is with him in being she is not near as needy or bothersome with him. If I try to take a nap or sleep in, she will most times, knock on the bedroom door because she wants me to get up with her so she doesn't have to be alone in the living room (less than 10 ft away). I figure I am at her beck & call 12 hours a day, 7 days a week minus times stated earlier in this post. My fiance feels that with the fact he covers the house payment & utilities that $600 per month is reasonable with $500 of that going to him and leaving me $100 per month for whatever I choose to spend that on. My total payments that come out of this that are my personal ones (car payment, car insurance, cellular phone, two cartons of cigarettes, off brand about $63 per month and one additional small payment of $50) comes up to $428 per month. If my math serves me correctly, 30 days per month divided by 12 hours per day comes to $1.67 per hour. He had the house payment before I moved in a year and a half ago & I don't know exactly how much my presence increases utilities & I do know that I do not consume a whole lot in food. He started this last month after he stated why should he have to do without and pay everything. He had his mother recently pay his son $30 for sitting with her for 3 hours (1 1/2 hours of which she spent in bed), she was eating dinner as we were leaving that we made for her & night meds were ready for him to give her, all he had to do was make himself a dinner plate & heat it up. My fiance said he thought the amount was fair as this is a 21 year old sitting with his grandmother on a Saturday night when he would probably be wanting to do something else because he has a life.She just started adult day care for 4 hours per day, 3 days per week which the majority of the time I will take her pick her up. She pays for this right now out of her own money until the claim gets submitted to the insurance company she has policy with that covers this.The daycare charge is $9.50 per hour which my fiance told her was very reasonable for watching over her & feeding her and taking care of her. She does not qualify for any type of assistance as her assets are way over what they allow as well as her monthly income. She has 4 children. Her son, my fiance. A daughter who lived just a few miles away from her in Florida but didn't communicate with her for about 2 years until we moved her to the midwest with us from Florida & has called her twice during the last 4 months. She has two other sons, one lives reasonably close in Florida, but she hasn't seen or heard from him in over 6 months & the other one she has no idea where he is nor does anyone else. I don't feel like any of this is right & sometimes I really feel like a beck & call girl. I had a job, not the greatest job and averaged $1900+ per month gross. I have no insurance now either & am with her almost 24/7 always subject to being summoned. My fiance works hard & makes excellent money. I want to take care of her, but I really feel like I'm being short changed here and don't understand how everyone elses time is so valuable. She has taken over our home & I really am beginning to feel like a slave. I don't want to get rich off this lady, but I don't think this is fair. Her children will inherit everything. Sometimes I feel like I'm just building up their inheritance. I want to start a home business to earn income again & to have something to do for me for a sense of accomplish