I've faced similar problems and also was able to overcome a few of them. A few techniques that has proved to be efficient for me are:

• Focus changes even if you move a millimeter. I tried so hard to keep my body as stiff as possible but that did NOT work. So, I just let it go. I start by looking at the blur image through the viewfinder, slowly move forward and start shooting as soon as the image looks clearer, keep shooting and moving all the way upto the point the image becomes blurry again. Do NOT move using your whole body/waist, instead try inhaling and exhaling slowly.
• I always shoot in continuous mode which enables me to increase the chance of getting a better focused shot.
• IS wont work, nor will aperture control. So, you'll need to set the aperture before detaching the lens. I usually use higher than normal ISO to be able to use a higher shutter speed, thus remove any chance of shake blur.
• Not sure if you're using a reverse mount ring, if not, get one asap. It helps a lot and you can concentrate on things other than keeping your lens safe from falling.
• DOF stacking is another technique you can apply. Its true I wasn't able to plan and execute DOF stacking yet, but if you take a lot of pictures of the same subject, chances are you'll find a couple or two which you can use to stack and gain greater DOF.
• Use of external flash is also very helpful and let you use smaller aperture as well as higher shutter speed while keeping the ISO low. Generally you'd like to use a diffuser along with it. Use this link to get an idea about how to make your own DIY lighting setup for better macro shooting.