Not all derailer has B screw , cheaper the derailer less adjustment you can do to them. The 9 speed chain will be to narrow for your bike and will cause more problems for you instead of removing them for you. A 7spds derailer and higher will work better for you. the problem you are having is the gears ratio for the derailer , like your low gear is to big for the derailer to handle . you need to find a derailer that will handle it.