How to divide money for Mom and Stepdad's care?

Most questions on this forum from an adult child's point of view are directed at how to care for the surviving spouse who is usually someone's Mother or Mother-in-Law. In my situation I am the main caregiver for my Mother who has dementia and lives with me. However, her husband of 30 years, my stepfather, spends days at my house, watching over my Mother and assisting with her care when he can. I am disabled as is my husband, who has not been able to work for ten years, and for these reasons I want to get help into my home, both to help care for my Mother and to help maintain the home because I cannot do it all any longer. Because my Mother was tenacious and always "watched" their money my parents have some money set aside for their needs and care while because of certain unforeseen circumstances even though my husband had a high level corporate position weI were forced to go through our entire retirement "nest egg" and live paycheck to paycheck. We have stated many times that selling our home and downsizing would make us more comfortable in many respects but it is nearly impossible to sell our home when my Mother and stepfather take up so much of the day to day living space. My stepfather seems to want to save their money for his long term care (he is 76; my Mother is 86), and I worry also that whatever funds they have will go for the first six months of the nursing home costs when the time finally does come when we can no longer care for her at home. Even now it is a struggle because of the severe limitations on my back and my husband's and only recently a hernia suffered by my stepdad. Both my brother (who nearly died two years ago when his intestines exploded, necessitating three major surgeries and leaving him with a great deal of debt) and I could use extra funds badly for things like personal physical therapy, dental care, as well as other doctor visits. I would like to have a person in to help with my Mother so that she is regularly bathed for instance something I cannot do alone. How can I convince my stepdad to cough up some of this money for these necessary expenses? If it were not for my Mother my stepdad would have remained a free-wheeling, free-spending bachelor with NOTHING SAVED or the other likely scenario, married my Mother and still continued his habits as a big-time spender. It was my Mother who banked his paychecks (and hers as long as he "let" her work) and gave him an allowance, doing without and saving for their old age, and now that dementia has taken away any pleasure in a home and/or nice clothes I want him to use at least half of it to benefit her, making her life as carefree and as comfortable as possible! We can't see eye to eye on this, and believe me I cannot take the stress much longer. I cook separate meals every night for my husband, my Mother, my dog and my cat (well, the cat is easy just open a can!) In addition to three bad lumbar discs have polymyalgia rheumatica and arthritic fingers and wrists and I need a rest. How can I make my Stepdad see that he should talk to an elder lawyer; and hire extra part-time help to spell him and me with our caregiving responsibilities; that he should get a checkup and take better care of himself; and a big thing, cough up some funds to help maintain my house so when the time comes I can sell it quickly and move back to the West Coast. This has been a dream my husband and I have shared since we elected to move to N.E. Florida in 1999 just to help my Mother and stepdad get settled in after he (my stepdad) took early retirement in order to please my Mother. Thank you all for your help.