Hardcoded limits :

ARELOC PRELOC BRELOC et.al.
Runtime relocator max segment size  : 33022

NLINK65 (all of these per object module)
Max number of segments              : 65535
Max number of open references       : ca. 20000
Max number of linkable symbols      : 65535

Softcoded (#define) limits:

NASM65
Max number of floats after a .FLOAT : MAXFLOAT
Max number of code bytes in object  : MAXMODULE - DEFORG  (curr. $EF00)
Max number of code bytes in com     : MAXMODULE