The short answer to the "can I tell" part is yes and no. Stepping back, fixing converts the remaining silver halides in the film to another compound that can be washed out. What it produces is a couple of different compounds, one soluble, the other not. If the fixer is fresh, the reaction will be pushed to producing the soluble version; if not, the insoluble. Think of the effect of burning charcoal - enough oxygen and you get carbon dioxide, not enough and you get carbon monoxide. The same but different in a deadly way. And the fixer alternative is a sulphur compound that can react eventually to stain the film. The film might not be milky, but it ain't fixed! So, milky is not completely fixed, and, in the worst case, clear is fixed but will stain later or sooner.
If you remove the film from the spiral, you can still reload while it's wet by doing so in a bowl of water - the water will act as a lubricant, and you'll find it loads.
If the film appears speckled, refixing in fresh fixer should work OK.
The old "double the clearing time and throw" was intended to have fixer discarded before too much by product built up to impede the proper fixing. The insoluble compound is the reason behind the counsel to use two fixing baths for prints, as fixer in the paper base takes more shifting than fixer in the emulsion.