I would think you could just replace the $ with a label defined on the same line.
00001$:
jnb T0Full, 00001$
Note that according to the SDCC Compiler User Guide:
All labels defined within inline assembler code have to be of the form nnnnn$ where nnnnn is a number less than 100 (which implies a limit of utmost 100 inline assembler labels per function).
As for the other compiler warnings, those are symbols that assumedly haven't been defined anywhere. How were they defined in the original C51 code?