No, you can not debug with the break point as far as I knew it. Because, it has to be linked to the ABAQUS .CAE to run the subroutine, in which can not be interrupted when it is running.
However, there is way to debug it. The way to debug the UMAT file is to use the following fortran code:
print *, 'sth to be displayed at log file:', values
at each line of virtual breakpoint to display the desired outputs. The output will be written in the UMAT subroutine log file generated by the ABAQUS. Although this is troublesome, it gives some useful feedback while you can control the debugging UMAT file.