Can you use live-view x 10 magnification?Some of the lack of sharpness is me being blind as a bat and guessing when its in focus,
If you don't use it already, it's probably the best way to focus a manual lens on a DSLR.
I also use the same technique for focusing at night. I'll open the lens wide as it'll go, bump up the iso as high as it'll go and then go to live view and manually focus the lens with it on x 10 magnification. Then switch live view off and readjust my settings to what I want them to be.
I'm long sighted (due to age) so can't see things clearly close up, but can - without glasses - when I use this method.