Hi there....I've worked in acute medical rehabilitation for about 20 years now........

......and wouldn't do anything else. The facility I worked at previously had staffing ratios about the same as what you are talking about. We did have more CNAs and that does make a difference. The facility where I am now actually has a lower nurse patient ratio (5:1). We are a "combo" center....we have all types of rehab diagnoses. We still have at least 2 CNAs/PCTs when we have 15 patients (we have a total of 25 beds). Personally, I have no problem handling 6 or 7 rehab patients, because they are not on the unit all day....BUT that is with the back up of well-trained CNAs and help of therapists too.
What is really unacceptable about your situation, to me, is the lack of equipment and training. ALL rehab staff should have
extensive training in patient transfers.....how do you reinforce what your therapists are teaching patients and families if your nursing staff doesn't know how to do them correctly? And there's the issue of staff injuries. Then,there's the issue of lack of equipment. Hoyers are really a necessity in this day and age of the morbidly obese and extremely dependent patients that we are getting in rehab. There are also sliding boards. If used properly, they are
great back savers! BUT, it takes practice to learn to use them correctly.
As far as your own back problems......rehab is physically taxing because it takes the whole team working together to provide these patients with the most thorough rehab experience. Even if you had a Hoyer lift, you still have the issue of turning and repositioning patients in bed. I'm sure I'm not telling you anything you don't already know...this can really put a strain on your back. If you really are set on continuing in rehab, I would say YOU need to be proactive and keep yourself as fit as possible.....if you don't already have a personal back program, get one of your physical therapists to design an flexibility/strengthening program for you.
I certainly hope things work out for you and for your unit.